I ended up purchasing a rash guard for the race. It's the same blend as all the tri tops I looked at and it's purty. I have a huge back piece that I was nervous about leaving out in the sun and the rash guard has SPF 50+ built in. I ran in it today - no chafing, but it was a bit warm (then again, I was running on the beach in Florida, so that doesn't help, lol).

I wouldn't do anything longer in the rash guard, but hopefully it will be fine for the sprint tri.