It's extremely rare that I have both feet on the ground at any point during a ride, so standover isn't something I pay the least bit of attention to. When you stop, you generally should have one foot on the ground and one on the pedal, so you'd have to be on a seriously mismatched frame to experience standover issues in a real world situation. I go by TT length and have never had problems. The couple times I went by standover (when I was younger and dumber), I ended up with frames that were too small.