I ended up opting for a 268xp full circle piston like this
While I like the standard windowed piston, I like the added stability in the bore that a full skirt piston provides as well.
I did a muffler mod on the 670 as well. I used a double cut carbide burr to create a 5/8"×7/8" hole in the front of the muffler and wire welded on a piece of 3/4" tubing cut on an angle. Finished it off with a few coats of Rustoleum 2000° high temp paint. I like how it runs.
I got new intake gaskets in for the 630/272xp build today. Installed them and she's good to go with no more air leaks.
Comparison videos coming...