Hmmm, not sure how different the tunnels are, but using the same measurements as the EDGE might be throwing things off. There may be numbers out there specific to "'skid X' to 'chassis Y,'" but it's hard to find anything on that, and they're only as good as the person who comes up with them. The templates I was thinking of based everything around a line parallel to the ground with the sled at ride height, centered on the driveshaft, and measure up/down from that line, not the tunnel. If I remember right, the front and rear skid mounts should be level with each other with the sled sitting on level ground.
Anyway, that's all academic without the right measurements. What I was suggesting was to drop the rear mount, which would tend to raise the rear of the sled and make it heavier on the skis. By softening up the rear springs, you might be able to find a spot where it still rides acceptably, but doesn't hit the tunnel anymore. One thing to keep in mind, it may be that the skid is mounted correctly (or close enough) in terms of geometry, but that the additional length is what's getting you. If that's the case, then you're looking at either limiting the rear travel or moving the skid mounts again (which would throw the front/rear balance off). To get that much track to work without trade-offs may take more of a mod approach (extended chaincase and/or drop/roll combined with more height in the front end), but I've never stuffed that big a track under a mid-length sled; maybe someone who has can give you some more specific guidance...
