The 5 wt handled both the salmonfly nymphs and dries very handily. I also fish it sometimes on the main stem of the Delaware, although there are times I go to a 10' 6wt.
Also, do you remember if wt. 4 you had tested was fine for small flies and moderate winds ( up to 15 mph) ?
It's been 10 years, but it seemed to me that it would. I don't know if he's changed his policies, but every rod I've gotten from Kerry, we've talked about it first on the phone. And in the instance of the 5 wt, he was happy to ship me 2 (maybe 3) rods to try. If he still does that (and you're not in a rush) that might be the best.