The MAS cabs don't lose low end to the same degree, when elevated, as other cabs do. I've found that my 46 generally works better elevated (too much low end, if anything, when set on the floor in its normal, horizontal orientation -- vertical is fine, though) but I never elevate my MAS 112 and it sounds great on the floor. I also thought that the Bodai 110 I played at Mike's place sounded great -- open, natural, and well-balanced through the registers -- on the floor. I'd be curious to hear a 28 the same way.
I recall trying the two 18s in different configurations -- thought maybe we tried them on the floor, too -- I know I played one solo, on the floor. I can tell you that the low end was anything but lacking when set-up the way Mike described. B-string response was off the charts.
@BostonJazz72, do you have any difficulty monitoring your sound when standing right on top of the cabs?
I wouldn't be surprised if the 18s were easy to monitor up close, despite being small/low, but I haven't owned one and can't say from experience.
If you're looking at a 28, Kirk (whether the MAS 28 or the Bodai 28), you might also consider something like an Ampwedge (big, foam wedge to angle up a cab -- you could also use a couple of big doorstops or a sneaker, if it suits you). Aside from angling the cab up, it will be, in terms of coupling, somewhere between having the cab flat on the floor and elevating the cab on a stand (I've tried it with the 46 -- also when using my AK Hathor 1203 with my MAS 110 sub).
If using two 18s and you did run into issues hearing yourself, perhaps one could be set on the floor, facing forward as normal, and the other on its back, in the "monitor wedge" position. Mike, Stephen -- any thoughts as to how that would work?