Just wanted to post the solution for the record. I purchased a Fuel Safe check valve and installed in in the filler neck overflow line that normally dumps behind the right rear wheel. It had to be mounted right side up to breathe correctly and not interfere with venting. So as the photo shows, I made a loop and routed the "air intake" back down below.
Results, two track events .. no spillage, no fuel starvation either .. but I'm not sure that this solved that. See the photo.
Sam
