Specs show RMS @ 300watts... I do need to switch to LEDs, though the stories of having to replace the stator are making me consider adding an extra rechargeable battery...
Forget the power output spec, it isn't useful for this at all. find out the actual current you need to run it....turn it on, crank it up and see how much current the system draws in the 12V input side.
That is the REAL number you need to look at.
Once you know that, you can calculate if the bike can handle it by reducing current draw on other compunents.
Remember the system draw I am referring to is NORMAL useage of lights and electrics when the bike is running.
The power in reserve that the R/R manages by either using or shunting it to ground is basically stuff like blinker, flashers, horn, cooling fan, brake lights, high beam, ..and others that are not normally on, and not all used at the same time for extended periods.