I've been flying mantis for about a hundred jumps or so, and there are lots better mantis flyers in here than me, but here's how I learned. First, I was very lucky in that a friend of mine who has done a couple years of four way (who, for the sake of this post, we'll call "Karl") and his wife (who we'll call "Cherie") gave me tons of help with flying mantis, as well as 4 way coaching in general, and I was able to ask them questions, and did allot of 2 ways with Karl in which we just worked mantis. Obviously, the tunnel is the best way to learn this body position. However, I believe the second best way is to do 2 ways specifically focused on mantis flying, preferably with a coach and video, but even just with another stable faller to lay base is better than trying to learn solo or in larger formations. The problem with solo jumps is that you have no frame of reference to your turns and slides. The problem with larger jumps, or even 2 ways not focused on mantis, is that while you are worried about turning points, maintaining eye contact with your clone and other cool, fun, important belly flyer stuff, its almost impossible not to slip back into the position you find most comfortable and easiest to fly, often without even knowing it. So I found that doing some mantis specific jumps made it much easier for me to transition to that position. As far as ground training goes, for about 3 months I religiously got on a flat bench 4-5 times a week at the gym and practiced mantis turns. I would hang my chest of the front of the bench, raise my shoulders, and spread my knees out past the side of the bench. Then I would kick Mantis center turns, usually in sets of 40. I found it to be a good lower back exercise and an easy way to work up a sweat. (A word of warning: if you are a dude, it is important to make sure the jewels are pointed south during this drill.) I think doing this helped me get down the muscle memory for flying mantis, and once I started the position, I never really went back to flying a box. However, when I did finally get to the tunnel I found 2 problems- 1) I had my legs spread to far apart. 2) I was using much larger inputs than I needed. Since it seemed pretty obvious to me that these were habits that I was reinforcing with my drills, I stopped doing them and just switched to back extensions. On a related note, I would recommend some kind of lower back exercise to any type of jumper, but most especially to my fellow belly flyers. Helps allot with that next day lower back soreness. That and stretching. Anyway, back on the subject, Karl does his mantis drills in a swimming pool. This might be more beneficial than what I was doing. I asked Thomas Hughes what he thought about ground drills and he said that they had limited use early on, but that you have to get into a column of air and drill in order to relly learn to fly the position. Hope that helps.