Phil, I'd suggest sending them to JH Audio for adjustment, otherwise you'll keep thinking about the fit all the time. I think I got pretty lucky the first time around as I don't experience any discomfort or left/right balance problems. Isolation is a bit less than Etymotic ER-4, but at the same time it's more than enough even in very noisy situations (metro, bus, etc.). I tried the Sensaphonics test and both tones appear pretty much at the same volume for me.
I had not used my JH13 for a week, now I'm listening to an awesome trad folk album and man do these headphones sound great.