I don't think a TAGish player will be c/c a lone heart draw very often at all. 9h9x, 7h7x are possible, but a very small chunk of his range. I really feel like the majority of his range that checks this flop is either giving up or is a range of better hands or better draws that are killing you equity wise. I'd probably go ahead and check back. The only real merit to betting the flop here I think is to protect vs random overs that are giving up, given he's utg though I think his range is strong enough to include enough big hands that our bet will be -EV enough for us not to want to worry about protection.