Ive had my 425 a yr now and Im upgradeing to the same exact scorpian equipment you are .
do not put the gear on without dremeling a flat area these motor s spin up at high rpms and if it slips you might burn up the motor and even loose the 425 if the gear slips in flight.
Now on the bec question I run mine sperate - I just feel safer knowing I have it on a sperate bec that's my preference and its giving me all the power I need to the servos and gyro. I tried runing my sbec off the esc(eflit 60amp) as a trial run with my original bec not (scorpian) and the power to the servos and gyro didnt seem right was not responseding correctly and when I switched to a sperate bec it was fine.
well give it a try see what you like
and fly that 425
