I had great service from Bendpak. Brian Lockhart at asedeals.com (although based out of Connecticut) not only provided the best price from anyone, but had great follow-up customer service when I discovered a couple of problems with my order. He'll very straightforwardly answer your concern about lift capacity based on wheelbase.
I went with the HD-9XW for a few reasons: I was looking for a wider lift to fit a boat trailer beneath whatever I was storing up above; I wanted the maximum height possible, as I wanted a Defender to be able to clear the ramps if something else was stored up above (frustratingly, the 2-post lifts offer little in the way of height); and, of course, capacity. I have no trouble storing a Defender 90 at maximum lift height... so far. I seem to recall sharing your concerns about the length of a vehicle, but something put my (rather paranoid about personal safety) mind at ease.
I have to say, for routine service work, the 4-post design isn't ideal. Again, the 2-posts out there don'f offer much in the way of lift height... but, I have grown to appreciate some of the options that are unique to the 4-post design. Simple when you're just shuttling cars in and out for storage - no need to bend down to adjust arms; the ability to stand on for access to heights (in my case, I have access to a storage space by climbing a ladder and stacking things like tires on the ramps); and low ground clearance cars are easier to lift (although I've sold my Porsches, it's a life-time purchase... fingers crossed that I'll again have something with only inches between ground and exhaust).
Lastly, don't cheap out on the 110v like I did... it's exceedingly slow. Oh. And also budget for a compressor drier. I made mine out of various parts - but Bendpak won't warranty (especially the slide jack) for moisture damage.