Ultimately, the answer above was close enough to be reliable. However, I really wanted to know for sure and so it made me do some more research. My initial question was hoping that someone had already figured some of this and I wouldn't have to start from scratch. Here's what I found - hopefully this info will be of some use to anyone else who might need it.
Alternator output is rated at 329 watts @ 5,000 rpms. Obviously, you're looking at a little lower output at idle in traffic/stop lights/etc...
If you run both hi and lo beams, brake lights and turn signal at the same time, with the few other electrical components I can measure, you're looking at a draw of just under 190 watts. Things like the instrument display, fan motors, fuel injection, etc. I can't find specs on. They've got to be small by themselves but they also add up all together.
My Gerbing jacket liner is rated at 83 watts. This pushes total usage up around 270 watts. Gloves would obviously add more (20-30 watts).
I'm going ahead with the install of the harness for the jacket liner. I'll include the list of individual specs below for anyone who cares to keep reading. For the SP2 specific ratings, SP1 is slightly less.
Lo - 55w
Hi - 55w
Brake lights - 23w x 2 (SP2)
Tail lights - 8w x 2 (SP2)
Turn signal - 23w
License light - 8w