When I started shaving with a straight, I read somewhere that someone recommended beginning with a 5/8. I followed the advice. Since I was concerned about a lack of dexterity I reasoned that a more narrow blade would be easier to work with. Since then I've purchased several razors, all of which have been 5/8. The only change that I made is a switch from full hollows to half hollows.

A week or so ago, I decided that I was going to try a 6/8 half hollow. I ordered a couple, and they arrived today. I just shaved with the first one, and am now thinking about selling all of my 5/8s. It is amazing how much the little difference in weight and stiffness makes. It really seemed to smooth out my passes. Now granted, if I had superior technique the difference probably wouldn't matter as much, but the difference really works for me.