good enough snag free shunt 

got good enough shunting without snags!
The formular that makes this work is that the mast is a little taller than halyard attachment point on the yard. This means that when you bring the sail in to the center it hangs above the deck and doesn't snag on anything. This also means that when sailing, the yard is closer to vertical than the mast. If you look closely at videos of marshal islands proa, you'll see that they use the same geometry.
However, most western adaptations of the crab claw seem to miss this and use a longer mast that stays closer to vertical. This means that the tack must dip below the deck during the shunt, snagging on the aka ends, the mainsheet, and anything else in the way.
By the way, the mast stays are not tied to the mast, but slide through a hole in the mast head, with two stopper knots so that the mast can move, but not too far. Also, they are from nylon to allow some stretch.
Also, I've abandoned the double ended mainsheet, that went around the mast (and tended to snag) to a marshallese style single ended sheet that goes under the shunt lines. I think the easiest method is to start by pulling the tack back using the lazy end of the shunt line, then switch to pulling the working end when the tack passes the mast.