I've never tried a tri suit, but I am a big fan of just a sports bra and bike shorts under my wetsuit (for open water swimming) or alone for the pool, then just toss on a cycling jersey and go. I always warmed up ok, even on those misty WA days when the lake was warmer than the air...
Pretty sure the sports bra and bike shorts combo is not happening - ever. :) Was going to do that and the one piece suit. Should have stuck to that plan - peel off the suit and put on a shirt.
Well, I did mention there was a wetsuit involved, right? ;-)
Only in one scenario. ;-). Though, I do sort of admire those women who flaunt their rolls.