Hi Barry,
We have an RV-4 with the castoring tailwheel and I have done a few firm arrivals but we have never had a problem like yours. Where are you based, we are at Gloucester if you would like to compare tailwheels.
Meanwhile here is a photo after landing at Popham a couple of years ago. We probably only had 1/2 fuel but we are both 14 stone so it was a reasonable load. As you can see there is plenty of gap between the spring and the rudder.
Cheers, Alan.