DivingDreamer: My wife and I are going to be in SXM starting July 3 and diving the 5th with Dive Adventures out of Simpson Bay (probably more days after that too, but that's the only one pre-reserved so far). Maybe we'll see you there, depending on what op you picked! (We've also prebooked the Dive Safari's shark dive on the 8th). I'm 6'2", shaved bald, with a goatee and glasses, and my wife is about 5'8", blonde, shoulder-length hair
We did St. Kitts last year in June with 3mm shorties and were fine - our guide and some of the other divers were all suitless. We were planning on just taking our shorties down this trip as well, even though we hope to do some of the deeper pinnacle dives off Saba later in the trip (July 10-11). Neither of us is terribly skinny these days, but my wife is pretty cold intolerant and she was fine last year. The SKB dives were down to 60' max or so. Of course it helps that we've been practicing locally here in Texas in 3mm fulls in a spring fed lake with surface temps similar to down there (84ish) but thermoclines at 25ish and 50ish feet...
I'd bet given your experience in cooler water, a well-fitted 3mm shorty would be fine, and a full would probably not be overpoweringly warm unless you hate to strip it down to at least waist level on the surface between dives. So you probably can't go wrong either way. For that matter, in late June / early July a plain skin would probably be okay as well, but I kind of prefer the shorty at least, if only for the psychologically better gut-compression effect of neoprene over spandex.
RTRski
p.s. regarding gloves, I wore them in SKB if only for ladder grip, but I've read that some of the coral preserves don't want you to wear them as you might be more tempted to touch... was curious myself what reaction I'd get to them in SXM and Saba, but bringing them just the same. They can always ride the gear bag if someone gripes at me.