I've been reading reviews of the Seven Axiom and it's just a long series of poetic waxings about how sublime custom fitting is, the great difference a millimeter makes here or there, and how much lesser mortals are missing.

My LBS says that unless you are oddly shaped there is no need to go custom. That's one opinion.

Then there is what I gather just by thinking about it.

Successful brand names spend a lot on R&D to design an approximation to the ideal bicycle. To my mind there must be a combination of geometry and size that constitutes the ideal road bike. Deviate from that and it gets farther from the ideal. Therefore if you can ride comfortably a bike of geometry and size close to the ideal, that should be best. If instead you have to alter the geometry here or there to fit your body, fit it may, but that does not imply that will be experiencing the best ride quality. You can't.

What do you think?

I never had a custom bike. I am lucky that a stock Cinelli and a stock Cannondale CAADX fit me like a glove, but all these ah! and oh! about custom bikes have me thinking that may be I have no clue as to how much better it could be. Also, I gather the most custom jobs entail only minute variations of stock geometry (small corruptions of the ideal), and if that is the case why bother pay the high premium?

What's the low down on this?

A certain size and configuration of bike may be the mechanical and aerodynamic ideal, but it is no good if the rider doesn't fit it. Rather than having only one "geometry" rider in the whole world, cyclists compromise by fitting a bike to themselves as well as possible while preserving the important design and geometry relationships. The general opinion is that fit is paramount. Everything else is secondary.

There can't be an ideal bike for every person or situation. Everybody has different body proportions, different flexibiltiy, different strengths and weaknesses. Also a bike built to glide over chipseal and gravel probably will be different than a bike to race an 8 corner crit course. The bicycle is just one part of the equation, the other part being the rider.

And the funny thing is that you may not be paying a high premium for a custom frame. Many production frames are now as expensive or even more expensive than a custom frame.

The thing many people don't realize is the buyer of custom needs lots of riding experience on multiple bikes in order to help with the custom design. The builder, designer, or fitter can only do so much on thie own. The buyer needs to have some pretty definite opinions on what exactly they want and need so that custom completely fits the bill.

Custom bikes shine when your preferences stray from the mainstream. Perhaps you want some flex in your frame. Maybe you want to run wide tires with fenders. Maybe sometimes you'll take your bike on a tour. Or maybe you want integrated lighting so you don't have to worry about recharging batteries. Or perhaps you want all of the above. Production frames cannot offer this because these are niche preferences. I think fit is only a small aspect of the custom market. I'm willing to bet most people who get custom frames do it because their vision of a great bike is not met by the production options.

^^^
This!

Since stock frames fit you fine, a custom would be a vanity item and perhaps a luxury item depending on cost - nothing wrong with that, it's your hard-earned money. I think that a lot of people overfutz the whole bicycle thing - tubulars, material, aero, grams, black etc.

There's a simple way to find out whether a custom frame is necessary for a better fit than standard production: get yourself measured and compare the numbers the bike fitter gives you with the specs of the available sizes of the frames you like.

Yes, and be sure to have a good idea of how much deviation from ideal is reasonable. It is first important to understand how much error there is likely to be in the fit measurements. Measuring the human body precisely is very difficult. The error in the fit specifications could easily be several times the difference between them and what you find on a bike. So understanding how close you have to be and how much adjustment is possible with saddle placement and stem without compromising the handling of the bike to get a good fit is very important.

i have custom tailored clothing and i have off the shelf clothing and both fit me fantastically

my off the rack bike(s) also work perfectly

lucky me

If you're out on the tails of the bell curve as far as body size goes, then there's no doubt you can be better served by a custom frame. But in those cases, we're not talking about differences of a millimeter or two. I think in cases where "normal size" people buy custom, the ride and comfort they attribute to fit may actually be accounted for by the fact that they getting a frame tuned to their weight and riding style and often hand crafted from the best tubesets with no compromises for mass production.

It's likely a high-end off-the-rack frame in the same price range would ride just as nice. But when you reach the price range where custom becomes an option, the other advantages of being able to spec the exact configuration you want really sweeten the deal. When I ordered a custom CX frame, I was able to spec the tire clearance, cable routing, the exact braze-ons I wanted/didn't want, custom travel couplers (Ritchey top, S&S downtube), etc. I love the fact that I was able to get the exact frame I wanted with zero compromises. People who think fit is the only reason to go custom aren't seeing the whole picture.

When I ordered a Seven, I was interested in a reasonable light frame with a very stiff rear and bb. I didn't want it to flex when I sprinted or stood on steep climbs. I couldn't find anything stock that did it. However the geometry turned out to be almost the same as an existing stock steel frame I had. In comparison the steel flexed like crazy with the same effort though.