Considering Prometheus' reputation for strong products...
http://redwolfairsoft.com/redwolf/ai...te_Ver_III.htm
If a "stronger" tappet plate also fails, consider a flexible one. A very strong tappet plate would take the pressure unwelcomingly, and eventually would crack/snap. A flexible tappet plate would just absorb the punishment that a high-speed setup dishes out, although I'm not sure where to find something like that. At least, that's what logic would dictate.
This might also be an option.
http://redwolfairsoft.com/redwolf/ai...late_Ver_3.htm
After all the problems I had running ridiculously high-ROF, I just got pissed and dropped it for high-torque instead. I'll ask the people around here that still run their high ROF models and see if they have any specifics when it comes to tappet plates.