Hi. I currently at the max with my current bike. My current bike a 1995 Trek 950 I have road tires on. However I'm having fit issues. After 5 miles or so my arms get really stiff. I've tried a riser quill on it as well and still have issues. TT is 580mm with a headtube of 90mm, switched the original stem(120mm 10 degree rise) to a 40degree 90mm. Frame size is 18in and I'm 5'9" with a 33-34in inseam. I'm feeling the bike is too small but also that the bars are too low.
I'm hitting a wall at about 15 miles as far as my arms. I've done 30 mile or further rides before though(with a lot of pain). I'm not sure if a flat bar hybrid would be comfortable past the 50 mile mark which I would like to be able to do.
A couple bikes I have looked at are the
Cannondale Quick (appears shorter tt)
Dawes Lightning off of BD
Scattante W/R 350