TBH Will, I just built mine.
When I put the prototypes together, there was a noticeable high spot and I did blade the rack as it was the rack that was exhibiting the issue back then but the production fit and materials are much nicer.
I make you right not to want to sand it - you might be able to get a thin blade in there if you're careful but I didn't do anything and I can't notice any high spot now that the front end is fully assembled and being powered by a ridiculously powerful digital servo
We never experienced any issues during testing with the prototypes and since these are much nicer, I'm not expecting any now either.
Not sure if this helps but it is what I have done myself.