bottom:
5/16" bolt 2 1/2" or 2 3/4"
Middle (behind the headtube)
3/8" bolt 2 1/2 or 2 3/4"
Top (through the headtube)
3/8" bolt 2 1/2 or 2 3/4"
This fits with a little bit of grinding doing to the foldy rails and headtube. This way you'll have the steepest headtube angle (about 82-83 degrees) while having the most solid foldy possible.