as long as the belt is running straight... who cares.

You replaced the air filter?
Drained the tube under the bike? How did you decide how tight to get the belt? Can you twist it 90*?
A good piece of string under the belt on the front pulley, gotta pull the guard, watch for vibration damping pads, and run the string across the face of the front pulley back to the rear pulley.
That will show you if the rear wheel is out of alignment.
Gotta roll the bike till the string is on the front of the pulley.

Maybe just a straight edge on the rear pulley, look down it, see where it's pointed.

If you don't mind spending a few $$ this thing makes life really easy
https://www.youtube.com/watch?v=JKWHmlkp94U&feature=youtube_gdata_player

Sure you can. I can do it with string too, but I prefer this. It's quick, easy, results are repeatable and good for guys without the skills. Seen some pretty ordinary alignments done with string by guys who don't really know how. Using stretchy string, bending it around stands or exhaust, that kind of stuff. Can buy an inexpensive block and pointer kind of deal that accomplishes the same thing. Or you can make one if you have the skills to build accurately. They work well too. I doubt it would go over the Cabbage rear pulley though.
https://www.motionpro.com/product/08-0048