Sounds kinda like the worst of both world with how quickly the crosses of the MF frayed and broke.Try Velocity mains and MF in the crosses, with MF strung lower than Velocity. This is better than FB Velocity.
Or do the crosses last longer for you that way?
Anyway, I've 5-10 other multis to try in a full bed before I start experimenting with hybrids between multis.