How hot do these get, can one of you tell me?
That rectifier disipates all unused power as heat. It will/can get very hot. Take it's capacity (400+watts) and subtract all your electrical loads (battery charging, ignition, headlight, running lights, heated vest, grips, etc.) and whatever's left is dissipated as heat from the rectifier (think of the heat from that wattage lightbulb). The permanent magnet systems govern their output only by the RPMs of the engine thus all power must be disipated to somewhere either a useful load or heat.
Keep it in an cooling air flow or the heat may destroy it or something nearby.