No takers on that one... I left around 5/8"-3/4" if anyone is interested. I've also scribed my lumber over the axle hump, here's a pic:
https://goo.gl/photos/wfxEyC7z46JYLnePAOn the passenger side, the fuel filler neck for the 'under-bed' tank sits about an inch or so off the frame. I was trying to decide if I should cut a nice round hole to slip it through, or if I should do a inverted "U" down to the frame. The round hole would look the best, but I'm thinking that if I need to pull the bed off for any reason, a "U" would allow it to lift straight up.
Any thoughts/suggestions?