My buddy and I both did them on our Axys' this year. I used an IM2600 and mounted it length wise. Used 4 countersunk bolts to mount the case to a set of rails from craiggerbuilt and then mounted the rails to the tunnel t-slots with carriage bolts.
Buddy used the IM2450 case with Mountain Addiction rails and just used longer bolts through the rail mount holes and up through the case, with large flat washers and a lock nut inside. I like this design better as it cant be taken off of the tunnel if you lock the case. Mine could be taken (though I like to think sledders are better than that) but if you have your sled locked up at night it wont be an issue.
Ill post a picture of mine, and try to get one of his later. Not sure what there will be available for the G4 for rails beings the coolers have changed.
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