Loosen the air box but don't remove it. It will be a tight squeeze but you should be able to remove the small air hose and maneuver the filter on and then re-tighten everything. Tighten up the clamp and you can rest knowing that it ain't gonna come off. I would also disconnect the -ve terminal from the battery first because there electrics down around there.
You shouldn't be running the triple filters without the crankcase vent filter because you are allowing dirt and stuff an entry point to the internals of your engine.