One thing, if you want to play stock class with this, look into something that can fit over the top tube opening and slide back and forth. I played with one that I picked up a month ago. Didn't leak, surprisingly, but having to unscrew the feed plug, on a LB, load, and then close it can be a bit involved. That hole will make reloading easier. I am not sure about Mad having made any seal kits. I think that there was a crucial seal that he could not replicate.