I know that Blackspire makes a bash ring that mounts to the outside of the spider (and, thus, works with all three rings intact; it comes with extra-long chainring bolts). Just looking at my bikes, though, it seems like moving the big ring in should work, though you may want to flip it around for the best fit, which may mess with your shifting (shift ramps facing the wrong way). Also, keeping it in the normal orientation but on the inside of the spider may make for a weaker attachment, depending on how your chainring and crankarm spider interact.