This build has been going on for a while, on the sly. I've been discussing various parts of the process over on BNA, where, most importantly, nobody knows my dear wifey, so nobody could dob me in
Now collected all posts and built them into a build thread (on each board) for future reference.
I cropped down a picture of my current road bike, for another thread, but thought I could also post it here to justify why I've needed to go for crazy custom geometry on this disc roadie.
That's a 53cm generictaiwanesealloy frame (which DBR call size "S / 53"). I'm 5'10", and most simple height-based fitting charts suggest would put me on about a 56cm frame.
I need the small frame for the top tube length. Then I need a ridiculous stem to get the bars high enough (and quite a lot of seatpost to get the saddle high enough). This bike puts me in quite a low aggressive position - especially in the drops - certainly not up in the wind admiring the view. I'd probably add another spacer under the stem if the steerer was long enough to fit it (it was a second hand frameset, I didn't get the option of leaving the steerer long).
My other two drop-bar bikes - an On-One Pompino and a Long Haul Trucker - are both 54cm frames, and are both too long in the top tube. I use a 50-60mm stem on each of them to bring the bars closer, up on a big stack of spacers. The three bikes all end up with relatively similar bar position - the LHT is somewhat closer and taller than the DBR, and the Pompino is in between, but all of them are much closer and taller than I can get on a production frame using "normal" parts.
That saddle position on the DBR is universal on all of my bikes. Slammed as far forward as it will go, on a zero-offset post. I think
I'd like to go a little further forward still, but I have no way of trying it.
So, my custom frame will have a steep (75°) seat tube angle to bring the saddle forward, short top tube and long head tube to bring the bars up and back. I intend that I should be able to get the same fit position on the new bike as I have on this DBR (and the others), but with the saddle clamped mid-rail, and with a flat ~100mm stem. Like how normal shaped people fit on production frames.
From there, I expect to continue fiddling with my position... but starting from the middle of the adjustment range, rather than hard up against the limits where I am now on all of my bikes. I can tweak saddle position forward _or_ backward. I can swap in shorter _or_ longer stems (angled up _or_ down), I can add _or_ remove spacers. A range of adjustability that is unprecedented for me.