Can I use a Shimano chainring on an FSA crank, assuming both have 110 BCD? Are there any issues with the bolts? Are there issues with shift ramps?

I think they should fit but I've never tried that particular combination.

On Shimano chainrings the stamped lettering faces out (right) on the big ring, and in toward the frame (left) on the other ring(s).
Triple chainrings should be a matched set for best shifting performance. Doubles should also be a matched set but they're probably less critical.

On one hand 110 BCD is 110 BCD. All common cranks and rings use the same bolts and bolt circle.

But life is never that easy. While odds favor that any pair of rings will work on any crank, there are pitfalls.

1-some cranks and rings use a shoulder on the crank spider, with a turned ID on the ring, others don't. This can sometimes create a no-fit at the shoulder. It's solvable with a file, but if the arm has a nice shoulder to lean on, it's a good thing, and you want yo have rings that match. The diameters are the same, it's just whether you have that turned dimension.

2- there are sometimes variations in the position of the teeth with respect the chainring face. Doesn't matter if you replace a pair of rings, but can (pretty rarely) if you replace only one ring.

3- most 5 pin cranksets have the arm between 2 bolts. But a few use the arm as one of the mounts. The rings fit, but the small stop pin on the outer is in the wrong place. That's why some replacement outer rings have a threaded pin and two holes to choose from.

So it's probably OK, but there are some traps.

Of course, since I asked, I found FSA chainrings at a reasonable price. I'm just looking at going from a 36 to a 34 on my compact double, and then also a wider cassette in the back. I think the wide cassette will give me even more trouble than the smaller chainring.

The shift pin feature is on a big ring , the inner of a double doesn't need it, .. no 3rd ring to lift from..

Will the 50/34 combined with 13-29 give me trouble with Campy Chorus 10sp short cage derailleur? I'm looking to do this conversion for short term use. I regularly ride 50/36 with 13-26. I'm doing a 10,000' climb of Haleakala in Maui and want to train on the same combos I'll ride the volcano in. Once I'm done with this ride I'd want to go back since where I usually ride I have no real need for such low gearing. If I had to live without the big/big combo because of chain/der problems I could live with that. I also have 2 wheels, so I could swap while training, only taking the low when I'm doing the climbing training, but using the other for my normal rides. And really, with the time it takes to get to the extended climb I'm using (Bear Mountain), I doubt I'll do it more than two or three times. I'll also ride some up in the Berkshires, but only over Thanksgiving. My Maui trip is over the Xmas holiday.

I did Bear Mountain, ~5 miles, 1300' and 5-6% grade, in my 36/26 and it wasn't really hard, but Haleakala is longer and higher by 7x. 36 miles and 10000'. But the overall grade is about the same except I'm allowing for more variation.

I'm still on the fence about taking my own bike vs. renting. The airline will charge $200 r/t for the bike, about the same as the rental, but I would need a travel case. My experience with a travel case isn't good either, they're really big and don't fit in a car. You need a van, plus we're a family of 5, and the kids are all big. I'd have to make a second run to the airport to pick it up.

I'd just rent a triple-equipped bike, honestly.

There are at least a few people on this forum who have rented a bike in Maui for that ride... you may want to bring your own saddle & pedals but yeah, rent a triple.

Do some digging/posting to see who's already done it that can share some advice with you.

Saying the overall grade is the same is nice, but... 36 miles with no let up is a different kettle of tea. hopefully you can convince the family to drive up in the afternoon or do occasional sag for you. That road is definitely on my bucket list.

I already have a bike rental reserved, but they didn't have a triple. I was just thinking that if I'm going to equip my own bike this way, I could just take it instead.

And yes, I'm fully aware of what 10000' of climbing is compared to 1300'. That's why I want much lower gears. This will be the hardest ride I've ever done. When I was at the top of Bear Mountain I was thinking I could easily do it again. But 7 more times without a break? That's a scary thought. I've been reading everything I can find on the net about the ride.

I would not get too worried about that ride. My guess is that if you cycle frequently then you will be just fine.

I have done that ride on our tandem. We did not use the granny. I think you will be totally fine on a single bike if you have been riding some before the trip. It is not that steep. It is however fairly long.

It is a beautiful ride. I am sure you will enjoy it. I am jealous.

Don't forget to ride around the island as well. The complete Hana road is fun. Stock up on water before you head back on the desert side as there are no services on that side. We ran out of water. It is a must do ride as well.

In a word Yes, it's beyond the RDs capacity.

The take up capacity of short cage Chorus is 27t. There's a bit of wiggle room there, and I've gotten them to work up to about 29 or 30, but that's the limit, and you have to measure very carefully. ------ Your proposed range is 32t, and I'm pretty sure there's no hope.

BUT all is not lost.

Since it's only a short term deal, measure the chain properly to loop the 29/50 combination plus 1" working room. It's too long for the 34/13 combo, but you don't ride that anyway. With the 27t take up capacity, you have 11 left after using 16 for the cranks. So backing from the 29t, your chain should be normally tight on the 18 for sure, and maybe one or two smaller, so it's workable.

Remember not to shorten below the big/big +1" mark because the consequences of accidentally shifting into a combination which the chain can't loop is the destruction of the rear axle, and.or the RD, or worst. OTOH the consequences of shifting into one for which the chain is too long is a sagging chain. In a pinch you can even ride it that way, so no harm, no foul.