Re: Track-loc casters for a 4x12. Where to buy and how much
You have to drill 5 holes per caster, one large one for the "female" end to intrude into the cab and 4 to hold that "female" "cup" in. If you do it right, it should provide a decent seal, if that's what you're concerned about. Besides that, the large "cup" also holds the caster in, so the entire force of any jarring on the caster is not borne just by the screws, and the wood immediately around the screws.
My old Marshall cabinet had a caster problem, so it was recommended that I remove the mounting screws and turn the base of the caster 90 degrees. Once I got the caster off, that had been done... several times, and the wood was all chewed up from many different screw holes from surface mounted casters.
The wheels are at least 3 inches, I don't see any problem. The only problems I've ever had was that I had one, maybe 2 wheels split. Again, each of those cabs is around 90 lbs.