Looks like 1/4 to 1/2" should give me the clearance needed without significantly
weakening the baseplate and in particular the opening for the safety cables.
Ok, but what "reason" did either/both companies say might be causing the grooving problem. I personally would not feel comfortable towing several thousand pounds of anything behind my rig if the material being used was less than original specs.
Apparently another poster is also noticing a similar issue on his setup which makes me think a possible design flaw or poor matchup of the tow bar/baseplate.