I've never had the problem myself, but another van dweller approached me with her problem. For a former gal, I helped do her bed up like a porch swing, and that worked perfect for her, but this gal needed 4 way adjustments.
No problem, add a post to each corner of the bed, and suspend the bed platform from chains to the corner posts. Voila, this gives here 2+ feet of easy adjustment in every direction.
Another trick I have used in the past when helping others was to add slide lock tent poles to the legs of the bed, so that each leg could be adjusted separately, again giving 4-way adjustment possibilities.
Hope this helps...