I thought more folks were concerned with bending the frames, rather than mere rust. That's why so many make those frame box kits.. http://www.ballisticfabrication.com/...es_p_1820.html
Knowing you Dave I bet you'd be happiest just pulling the bed off for a couple weeks, so you can get a 360 view of the frame. You're welcome to borrow my bug zapper for a while if you want to get crazy and box it in..
82 fj40, 99 uzj100, 06 gx470
97 DR650, 05 525EXC, 06 TW200, 89 TW200, 09 TTR125, 07 TTR90, 07 CRF50