I realize I'm a little late to this thread, but here's how I set up my 250 148" mid-roof with a ramp. The ramp was made from (2) 48" wide x 5'-0' long sheets of aluminum with a two inch bend over each side. There are 2x2 aluminum crossmembers welded in. It folds in the middle and just clears the closer mechanisms in the top middle of the door. I had the ramp itself custom made from a template that I provided, however the builder didn't pay a lot of attention and I had to cut off the very nice mounts he had welded on and make up my own from angle iron. Getting the geometry right so that the aluminum skin laid down flush with the rear floor when open was a challenge. Plus, the thickness of the ramp had to be accounted for so the doors would close when it's folded up. I was contemplating the idea of using struts as an assist (the ramp's too heavy to manhandle without some sort of help), but then came up with the idea of using an ATV winch, which works really well. The winch cost about the same as one strut would have. I stipulated to the ramp builder that it had to have 1200 lbs. capacity, but when I first installed it, it bounced like a trampoline with just my weight on it. I bolted a piece of 1" square tubing to each side, close to the middle, that drop down by gravity as the ramp deploys and it now handles me on the bike without any issue. I just ride the bike in.
I needed something easy to use, without having to drag out some ramps and set them up. The van doubles as a bike garage as I work away from home for 4 months during the summer and take a bike with me.