never did understand why people got so worked up over birthsheets.
even if you built an electrical to keep everything rock solid at 14.4V right at the amp's terminals, there's still impedance rise to contend with.
likely an F motor.
however, I have late E motors that have the same top plate as the F series, but 20oz less magnet. at least that's what I was told when I bought mine.
more than a few friends up here have competed with the CF 4k. from friends in street to the Riprocks in extreme.
they don't seem to blow up any more often than any other amp. **** strong amps