Toptube requirement of being horizontal to ground level, that's pretty ordinary in stock frame size, too... even used older frames.
I've been riding titanium frames since 1996, other frame materials before and during all these years, too.
I started with an early 90's Merlin Extralight, next an Ibis Ti Road, a Sandvic, Bianchi Megatube, Merlin XLM Compact, Litespeed Tuscany, 96 Litespeed Blade, then finally settled on a 2001 Litespeed Ultimate in 2004 which still remains as my favorite ride today, over 30k miles ridden on it..
Along with the Ultimate, I have another 2001 Litespeed Blade as my current TT bike.
Last year, I bought a Lynskey titanum disc road frame for under $500, built it up as a complete bike with misc parts in my basement for under $1200.
It's a ride anywhere, put it away wet, forget it and ride it againt without washing kind of bike. Minimal care required.
With over two decades of experience in fitting hundreds of customers for to regular factory-frame-sized bikes.
Personally, with expections of those that have extreme physical body type and very specific needs (riding extra long distances or long hours, extended racing careers) to compensate; custom frames can be overkills.
