The model weighs 6 lbs and goes really good with the 61. It's an old engine with a ring, so a newer 51 might be about equal to it. I tried a 13-4 and a 13-6 apc and both were no good. The 12-6 is just right. Even if you went with an 11-6, you could probably get it to turn up enough to still be very strong. Let me know how it turns out.