Don't know anything about the HF one,
but the few grit boxes that Ive been around all needed some common "wear parts" ,
i.e. the gloves, window glass, nozzles
and of course whatever medium you use.
If you can, check for availability of the parts and if something is a "standard" size
or an oddball.
Maybe someone here knows if any standard sizes exist in these things.
A decent, steep enough taper in the bottom so that the medium keeps cycling
But that quickly adds height to the unit though.
A screen in the bottom to catch the dingleberries and keep them out of the gun
will save a lot of hassle.
Take a look at the door to see if it shuts snug, if not,
it gets messy and that fine grit drifts into EVERYthing around.
(common weather stripping can help there)
A vacuum hook up is awfully nice too.
An interior light is almost mandatory (in my mind).
A source of DRY air is a big plus for using the cab too.
Sorry for not having a direct answer to your question,
or if you've already considered all of what I mentioned.
just hoping to help anyone who's reading, with what I can recall.