What Andy said. I'll add that the way I design a frame is based on their bicycle position and I match the frame tubes to that position. I recommend you get a fitting from the builder or one he trusts that knows how to fit those that have a different body shape than when they were younger/fitter and no longer dream of winning the Tour. That fit becomes the basis to create the design. Now of course I recognize that getting fitter through cycling will change your position so your frame design needs to be able to make those adjustments. My guess is that your builder will place your handbars higher (at least as high as your saddle) and put your seat angle further back to make your weight more balanced over the pedals. A shallower seat angle will help take your upper body weight off of your arms and hands. Of course my recommendations are only guesses and not based on the information that can come from a proper fit.