'23 Scott Addict RC15, Di2. I know Di2 is less likely to drop the chain during a shift, but it has... twice. Both times to the outside - which is better than inside. My last Scott (2017 mech Foil) dropped the chain passed the OE chain catcher once. Took removing the non-drive side crank, nudging the spindle to free up the chain... on the side of the road.

All ^that^ to say, I think I want to add on a chain catcher before my chain takes that ugly bite out of the paint.

Any recommendations?

Side note: I'm following Terry's, with Better Shifting, guidance to dial in that front Derailleur

I;ve been using a K-Edge brand chain catcher with no complaints: https://k-edge.com/shop/chain-catche...chain-catcher/

Or put on a chainstay protector
https://thecyclistreview.com/chainstay-protector/

I think chain catchers prevent the chain from coming off the inside.
Sounds like you need to adjust your hi limit screw (if Di has one, I am still in the mechanical age).

Except he wrote that it's the inside that concerns him, not the outside.

want a simple, see-thru chainstay cover? Go to a Wrap Shop and ask for scraps of Hood Nose Cover material... then get out your scissors and trim up a free chainstay protector.

really? hmmm.. let's check on that... "I know Di2 is less likely to drop the chain during a shift, but it has... twice. Both times to the outside..."

Sorry for the confusion. YES - it has dropped the chain twice to the outside. I'm concerned about that and addressing it (hopefully) with some adjustments. But yeah, I'm more concerned about the potential for damage when the chain drops to the inside and passes the spider. That happened to me last year and to a buddy last week. Fortunately we were 2 miles from the end of the ride. He was on his second ride of a new bike. He waited, while I went for the sag wagon (my car).

chains can sometimes drop off the outside due to mis-alignment of the front der. cage... if the cage is even the least bit mis-aligned to the chainrings, it can cause the derail when shifting....

i watched a worn derailleur's cage momentarily twist out of alignment DURING shifting... not saying your der. is worn or loose, just adding that info to the thread.
that derailleur is now on it's way to being a brand new dryer, or computer case, or maybe a trash can..

i've also seen a heavily molested and badly bent up ft. der that would swing from "tail in" to "tail out" when shifted... it too has been recycled. the customer kept trying to get me to waste an hour or more trying to straighten it out.. then i told him my hourly labor rate as i laid a $5 replacement in front of him.. he opted for the used part.
the "symptom" of that bike was...chronic overshifting in both directions....

You missed off "which is better than inside". He goes on to detail a problem he previously had when the chain got past the chain catcher and jammed inside the crank, and a desire to not damage the paintwork, so yes, I think he's more bothered about the inside.

This is what the inside drop did to the frame. for the record, I've been riding forever, have a BMX, then MTB background. I'm definitely attuned to chain-suck (more in the BMX and early MTB days), broken chains, dropped chains, etc. - and IMMEDIATELY stopping peddling. So, this damage was done in the first 1/2 second.

... which isn't really a current issue with the bike in discussion...... and i offered a tip on cheap, flexible, easy-to-do paint protection in a previous reply.... which is nearly invisible when applied well.
which reminds me... i'm almost out of adhesive backed, flexible, clear plastic... and a few wraps of packing tape would work in a pinch... sure looks better than a hunk of old inner tube and 4 or 5 zip ties...

This, plus adjusting the derailleur limits (assuming it is 2X).

Agreed. If your chain is falling off the outside a chain catcher will do nothing to help

I agree. All three daughters bikes have these as do a couple of mine and they work. A couple frames passing through my shop had Deda Dog Fang Catchers and looked like they might work as well.

I agree with others that if the chain is falling off to the outside, it's an adjustment problem. But I recently saw this dual-side chain catcher from Wickwerks that claims to prevent dropping from inside or outside.

I'd try to address the drop to the outside first with adjustment of the front derailer. I run a triple and use a chain catcher to protect from drops on the inside. I set it up 20 years ago, works great. Good luck!

I've used those in the past, they worked well. I bought one for a newer aluminum frame and it fit the seat tube but the fat downtube stopped me from mounting it low enough.

I cut the tube into strips and wrap it, a lot neater than laying a tube on top of the chainstay, it quiets chain slap, also mitigates tyre suck. I have some helicopter tape somewhere, it's almost invisible but doesn't last as well IME; better for cable rub though, if I cared about that.

If you can fit it, I prefer the Dog Fang type (see Deda, but there are probably others). In my experience they're infinitely less likely to allow the chain to get past and wedge below. They're stouter.