Originally Posted by
cubewheels
Nobody will be comfortable riding in race geometry, the first time they do.
Comfort in race geometry will only come after months of training in that position. Before that time, You might deal with lots of pain.
If you already have athletic level fitness and no underlying medical conditions that would badly affect flexibility, the only rule of thumb is how determined you are in adapting your body to race geometry.
I was completely comfortable on my race bike, sitting on it in the shop on their trainer, perfectly comfortable. I was in my mid-50s. I'd ridden a race bike in my teens though it was a French-fit bike, really all there was back then. I wasn't a couch potato. I was active, skied, hiked. could easily touch my toes, had been riding French-fit bikes for 5 years before purchase. (French-fit = bars level with saddle.) First time I rode it on the road, I knew I'd bought a rocket ship.