About chain stay length, it has been my recent experience with the 2 cm extra length on my home made bike does not affect climbing at all. 43.5cm vs. 41.5cm.
In no way am I a strong climber, never have been. I spin up climbs much better than muscle up them. Almost always seated on climbs. On the mountain bike I am the same way and have never noticed any difference in stay length on different bikes when climbing.