Maybe I am not understanding what you guys are referring to, then. Terry is talking about the difficulty of getting levelling shims under the feet, so (as I read it) he prefers installing a level ledger board. For the ledger to affect the level of the tub, the tub lip has to be sitting on the ledger, no? The tub is either sitting on the feet or the lip is sitting on the ledger board. It can't do both. If it's sitting on the feet, then you have to level by shimming under the feet - what good is the ledger doing?
I can't comment on older models, the current ones with feet are what we are discussing. The local dealer, whose service manager was a former Kohler employee, cautioned that the current models do show hairline cracks in the bottom of the tub, usually around the drain. In fact they were adamant that I fill the tub all the way to the overflow and let it set for a couple of days before installing the tub deck (mine is an undermount) and surround, "just in case". My tub was nearly $2 grand (including their special drain assembly) with almost $8 grand of slab granite deck and surround walls, so it was pretty important to do things by the book and get the Kohler warranty. The service manager even came by the house to look at the installation before the granite went in to make sure that it was all "good" - per Kohler's instructions.
Again, maybe I don't understand your installation. But I found that that levelling the feet wasn't a problem.