Are you sure that is having such a big impact on your bowling? It may well be that your run-up doesn't generate enough energy to force your leg to go through with energy? I'm talking from limited experience, but I have seen several of your youtube bowling videos and what I noticed was that you were perhaps paying too much attention to small technical aspects and your bowling was suffering as a result. I have also fallen into this trap; trying to change simple things like the position of my front foot and then bowling badly when it was entirely uneccesary to make this change. Philpott makes the point that you should always avoid change just for the sake of change. The ideal leg spin action is as fluent as possible. Just run up and bowl. After that you fine tune it so that everything runs smoothly, like a well oiled machine. I highly doubt if your back leg dragging through is so important, although it might be, I wouldn't really know because I haven't seen those videos. My basic advice would be to forget about it, just run un with the intent to deliver the ball with as much energy as possible, (evenly split between putting revs on the ball and bowling it with pace, or with slightly more energy into either) up to the point where you are feeling "contorted" and like a whip that has ben cracked violently and with force, always keeping your eyes on your target. I prefer to keep my eyes at the perfect length if I'm bowling from over, and the batsman's head from around. I think looking at the level of the head is ideal because that allows you to bowl the ball directly at the eye level and dip it down. My back foot doesn't follow through at all sometimes, but I still get just as much energy on the ball without it. After you've let go of the ball, nothing matters except following through naturally and being ready for the return catch. Try not to worry about what happens after the release, but rather what you can do before and during the release to increase its effectiveness. Again, I did not see the videos, I have no idea what you should / shouldn't do to your bowling action, but my own experience is that the release and action that happens before it is the only important aspect of the bowling action.