I've used Landworm 12 on 15, 16 first try, mostly Bb. Level 14 Turtle was Jack 12 mbM, Metal 12 Bb on 12 prizefighter, and Metal bmb on 13 Pot of gold! I'm waiting now to get Centurion! Wish me luck, and I hope this will help others!
12) Metal 12 Bb
13) Metal 12bmb
14) Jack 12 mbM
15) Land worm 12 bM
16) Land worm 12 Bb