NitroSteel,
Don't take this as questioning your abilities; I have no idea how handy you are with such things. I've never made any wooden wheels myself so consider the below as just musings of a shade-tree tinkerer...
I think it would be much easier to make the wheels if you did them un-dished. The 6 degree angle will introduce some variables, especially if you're planning on heat-shrinking the tires on.
If you decide to go with the 6 degrees and heat-shrunk tires, I'd want to be sure that the angles/diameters of the holes in both hub and wheel segments are uniform and centered/matched on the parts, and that the pressure applied to the spokes is the same on all as the tire cools. This will require some measure of precision and uniformity in all of the parts, as there will be a lot of pressure applied to them by the tire as it shrinks that will tend to push things out of allignment. Getting the right amount of shrinkage might be hit-and-miss.
You might consider either making the spokes straight, or assembling dished wheels with adhesive and add the tires without shrink-fitting them.