An electronician at our club, have replaced the FET's in an LRP Sprinter - now it handles 6 turns motors without any trouble.
Unfortunately, he's left the club, so I cant help with much details. However, I do remember that the FET's were in TO-220 cases and that they had very small raise time (dont sure it's the right name, but they were extremely fast switching on-of-on-of). I remember he told that that was one of the most critical parameters.
Schumacher Mi5 - Sanwa MT-4 / RX-462 / KO Propo PDS-2123 - Nosram 5600 X-treme Saddle Pack - LRP SPX Zero/X12 17,5 - Nosram Stealth Touch Evolution - MAAS SPS 9250