well to sand the bonding faces I used 600 grit and a 90 degree jig. Unfortunately it didn't quite square off the edges as much as I wanted, it took away the laser uneven surface but not the 1-2 degree taper. When I was bonding I just squared everything off and used the welding cement to flatted the edges for me. through visual inspection I dont think I will have any leaks but only testing will tell