2
♠ It's very close to the dividing line for me. It only matters in two cases: pard is broke or pard has a near game try hand.
Broke: 4.25 tricks in
♠, 1.25 tricks in
♦ ruffs, 1.5 tricks in
♥, and 0.25 tricks in
♣. A total expectancy of 7.25 tricks. Useful fitting cards for pard to hold would be the
♠ Q or QJ (+0.5), the
♥ K (+1.5), a fourth diamond (+0.75), and the
♣ A, K or J (+0.75 or more). Pard needs TWO cards to make 3
♠ a 50-50 chance -- this is too much, I think. Of course, we may go down one in 3
♠ when they have a part score in clubs or diamonds, but they face an uphill struggle to find it over 2
♠.
Close to game hand: I'll bet that most games reachable only after this particular super acceptance will depend on the heart hook. Vul at IMPs it might be worth the stretch.
If you super accept with this 15 HCP (albeit a very good 15) hand with a useful doubleton, pard will learn to be cautious opposite the next super acceptance, and you may miss a game. Can one afford to play such a wide range of the super acceptance (16 dummy points up to 18)? How would you like to give up the 1NT-Pass-2NT (or equivalent) game try? Pard opens 1NT and your choice is Pass or 3NT.
1N - (P) - 2H* - (P) - ?
*: transfer to spades