I'm a few days late posting this, but added both six and four prong trailer pigtails to my SMB. So, now have the RV style for my car trailer and whatever, the six prong for the frigg'n horse trailer and other farm type trailers, and the simple four prong for my motorcycle trailer. So, I'm pretty much covered, trailer lighting-wise. I've tried adapters for years, but they never seem to work right (perhaps a turn doesn't work, or trailer brakes, etc.). Now, everything works as it should.
It takes a village to raise an idiot.