Now, note how the tank actually looks pretty indistinguishable from other grav tanks. I mean, the one thing that this screw-basing makes mandatory is flocking the base, but is that such a big deal?
Now, here's the magic. You'll need: a nut, and a bolt. Oh, and the flying base, some superglue, and some epoxy. Honestly, it's not that hard and not that precise. I favor JB Stick-Weld, and I grabbed a half-dozen nuts and bolts of the same size since I'd rather not spend time trying to sort out a half-dozen flying bases before each game.
Note the nut superglued to the spot where the flying base would attach. While this pic doesn't cleanly show it, there's actually a mound over the base of the bolt. There's also a wash of black paint over the bolt, to dull the reflectivity some.
I've reversed the flying base to better show the small mound of epoxy. You see there in the middle? That's the bolt, held in place by superglue. Now, notice the grey area? That's a mound of JB Stick Weld holding the bolt in place. Then the third ring? Flocking.
The one way you can break this easily is to screw the bolt in too hard. Then it comes out the top, and pushes the nut away from the grav tank's hull. Then you need superglue to fix it, but it's not like that's a MAJOR fix.
I don't do this on my Seer Council as they're pinned, small, and I can get away with it. When I get around to building up Vypers, I expect I'll be using a thinner bolt, as it'll probably take more effort to hide it.
I also intend to carry this forth on my Tau army, as I like the low hovering look more than the stupid landing gear. They're HOVER tanks. They HOVER.