I have an OS 1.60 in my Sig extra. I have had best results (for IMAC) so far with a Pro-Zinger 18x6 (after break in). I think it gives the best scale speed and pull for my dollar. I saw a H9 cap with OS 1.60 at an IMAC meet and he was running a Mezjlik 16x10, but it looked like it was flying too fast for me. I have also heard of someone using a Mezjlik 20x6...?