So.... I took the airbox out, hacked it up with a rotary tool, and then used a fiberglass repair kit (resin and woven fiberglass) to cover the open area near the battery. I didn't really have to close it up, but I figured the less dirt that can get into the filter area the better. I then coated it with flex-seal to make it black and to close up any voids that the fiberglass missed.
All this cutting allows the airbox itself to sit 1.5" closer to the front of the bike. I had to make an extension bracket for the rear mount and drill two holes and mount it with some 1/2" spacers.
Finally, you can see what I've done for my air filter here:
It's a 1 3/4" hose, 1 3/4" hose coupler, and a 1 3/4" foam UNI filter, with significantly more surface area than the stock filter. You can also see my crankcase breather peeking out from its new home. It has a 12mm hose coupler connecting the hose to the breather filter. All are oiled with Jeg's air filter oil, which came dyed blue.
My suspension is at the normal level and I have no wobble, no tire contact with anything under the bike, and I can run big tires on the back with no problems now. The only detriment to this is my maximum water crossing depth has been reduced significantly.
So, why did I hack up the airbox at all? Why not just remove it? Well... I looked into modifying a hugger rear fender to fit the RX3, and I looked at using a mudflap to create a new inner fender, but when it came down to it the stock airbox forms the rear fender and if I cut it apart I'd be able to protect my new filter from road dirt from several different sides. That's why I repurposed it.
If I start going on super deep water crossings again I'll have to extend the silicone line and basically build a snorkel.
Charles.