Mel,
I would go ahead with the light topdressing, just be sure to water in right away and not let it sit on top and get hot. I did the same last Thursday up here in KC. My personal opinion is that as long as your aren't working the sand into the canopy in an abrasive manner (draggin, rolling, etc) that the benefit of the sand outweighs the possible negatives in this situation. I went about 1 hopper in my Tycrop per every 3 greens (probably a little heavier than I should have) and have seen no ill effects other than trashing the bedknives on one of our greensmowers.
Our temps have been upper 90's up here as well and I see the same thing in regards to a little scalping when it gets hot and humid like this. I am growing penncross/poa on old (some pushup, some sand based) greens and just raised heights late last week to .140" on grooved rollers.
Two other things I am sure you have already thought about, but when scalping has gotten worse in the past I have made sure that I am running the thinnest bedknives possible (hence the little bit of sand trashing them) and also have gone to solid front rollers (not at that point yet this year, but thinking about it). Good luck...I have feeling in we are in for a nasty rest of the summer!
Steve Wilson
Meadowbrook Golf & Country Club
Prairie VIllage, KS
swilson@meadowbrookcc.org