17 and 29 is... oof.
Regardless of the age of consent, this is an age gap where a power imbalance is not avoidable, and I don't really consider any relationship with an age gap like that... consensual.
I mean, you were asking in relation to Tapas' community guidelines, of course, and they will follow the law in this regard (meaning US law here), so I don't think there would be a legal issue.
Morally, though? Big yikes. 
Keep in mind the psychological development of a human brain is only finished once we hit 25 years or so, so the 2nd person is past that point, whereas the first is still in their adolescence. This isn't exactly... healthy.