I would like to see if it would be worth it to make our own wheel centers this year. My main concern is having a FEA model that does not properly represent the forces involved. I was going to model it using max normal force from load transfer, braking torque, and possibly the reaction from the tire lateral force. Anyone have any advice?

after a wheel centre failure in 07 we have spent a lot of time on wheel centre fea this year.

In terms of loads quite often stiffness or fatigue criteria are dominant. The loads we used are something like 2g cornering and 600nm torque (from TTC data). These are both unrealistically high giving the wheel a fatigue life far in excess of what we need. (as long as the castings are good enough).

The toughest thing is to constrain the centre correctly. The method we derived was an ansys workbench assembly. Including the hub with nuts, lumps of metal representing wheel bearings and a rim model.
The wheel bearings were constrained and loads applied to appropriate faces on the rim (be careful with this).

I hope this helps at least a little, feel free to ask me more detailed questions here or by email. Our centers can be seen on the last page of the "status of you car" thread. Zero compliance issues so far (front caliper has less than 2mm clearance) we will perform so fatigue testing on spares later possibly.