apex seal reversal...

[NoDOHC]

IMO, Make him upgrade to 2-piece.
3 piece seals in a bridge port engine just doesn't seem safe.

Unless its a shity motor an he wants to destroy it.

I have to agree with N. RotaryTech, I only reuse 3-piece seals on NA engines. My '88 13BT had 80,000 on the clock when I tore it down and the top apex seal had worn significantly on the side (not the face) until it was triangular. I have torn down 150,000 mile NA engines that the 3-piece seals were completely intact and still met tolerances, but not so the turbo (I have only ever rebuilt one turbo engine, so you will have to forgive my lack of experience to draw from there).

My 4-port has new 2-piece seals ($60.00 each from the Mazda dealer) and makes excellent compression (120 psi front and rear). I have not seen many 3-piece seals make that, so I am not sure that they are better. Plus the 2-piece seal is deeper and has more support against side loads (avoiding the triangular wear that I observed on the 13BT).