Since I traded my shortbed DC for a longbed DC, I don't really need my 18" extended pin on my 5th wheel trailer anymore. However, I only have 20" from my bumper to the trailer's lower front section with the rig inline. If I go with a medium extension, I'll only have 10"~. What's the minimum clearance before you risk hitting the trailer with the bumper in turns and going over hills and driveways etc. ? I've seen some that are pretty close but never measured. I'd like to go with a shorter pin for less stress on the trailer and less likely to walk into it in the dark when we're not hitched up.