I don't think there's any perfect solution.
I went for CMC bases after reading complaints of FASP swivels not fitting properly; quite a few people have to spend hours filing to get them to fit, indeed there were a couple of forum members who had swapped their FASP bases for CMC ones and were happier with them. Also a friend of mine who drives a big motor-home had a set of FASP swivels on it and one completely came apart when she was driving it

which was the deciding factor for me.
That said, there is a slight rocking on the centre bolt (it's very, very slight to the point I'd say it was completely negligible, but maybe that's just mine) and the safe did rattle like mad, but I stuck some lining carpet on the back of the front panel of the safe and it doesn't make a sound anymore.
Just in case you weren't confused enough I: