Wheel Alignment

I recently changed parts between the 2 XB-600's I've got to make 1 great bike. I learned (the hard way) that though both bikes look the same, some of the parts are different. Differences I noticed range from: rear wheel configuration & parts, front shock size, tube size, etc...

First question: Wheel alignment/placement: what is the best configuration with washers and such? Is there a mathematical formula or something to figure out how far forward or back the rear wheel should be placed? I've looked here and on other sites to find out what the correct alignment/placement should be but to no avail.

Second question: 72 volt mod: What parts are required to perform the 72 volt mod (i.e. mosfet, etc)? Would it be better to just purchase a 72 volt controller and if so what would the specs on it be (i.e. watts, etc)? Where may one purchase said parts and/or controller?

Third question: Breaks: I've used the spacers, washers and nuts on both wheels according to the directions and without the breaks they both spin freely with no wobble. When I attach the breaks and tighten them enough to make them effective they inhibit the free spinning of the wheels. Any suggestions?

The XB-600 with 60v mod has been great. I've enjoyed modifying it almost as much as riding it. I'm hoping that with the parts for the 72v mod I'll be able to repair the second bike; at the moment it's just spare parts in need of a working controller.

I look forward to your responses. Thanks for the help!

Eagleye