Actually, a external fet upgrade would be MUCH better than a internal fet upgrade, because the heat of the fets can cause the pcb board the radio and servo controller are located on to warp, this is a VERY well known problem in consumer electronics( it cheaper to build a thin board than a thicker one), especially in modern guitar tube amplifiers, which share a similar enviroment as the pcb the fets are around in terms of heat. To make a external fet upgrade, all you need to do is bypass their emitters ( what the motor connector is connected to ) a nd connnect the gates of the external fets to the gates of the internal fets, making sure the extrenal fets can be driven directly by logic level input, then you can mount the little heatmakers where you want( can anyone say "hood scoop", "intercooled" )

bob256