As mentioned in a recent thread, Main Vein has now got 2 distinct methods: V10, original crimpy, high rockover stylee - this is very obvious.
V8+/9ish using undercut (s) out left. I don't know the exact breakdown of this, just heard it second hand.
Don't think... I've seen this done a couple of times, and from what I remember it involves a high foot position, preceding a fairly wild slap. Katz does it in the new Amateur Hardcore film, but his beta will probably be stumpy specific.