i installed a namura piston in a 400ex shortly after i posted my message years ago. i sold it right after so never got a chance to test it out, but i did talk to the guy 3 years later after seeing him in a local sand pit, and it was still going strong, used the namura gaskets and valve seal kit also.

that being said i just installed a new wiseco piston in my trial ported blaster. go figure!