Vertical Open Crawlbot Style

Hi folks,

I'm thinking of building a CNC router in the crawlbot style, but hanging vertically to minimize space. The object would simply be to cut parts entirely out of MDF or plywood, no vertical adjustment necessary.

I've seen Maslow, which is awesome, but I'm doubtful of its linearity up at the outer extents.

Has anyone considered an open source "walking gantry" style CNC router? I'm interested in hearing your ideas, good or bad.