I've done that. Sorry no pics of the process.
http://s305.photobucket.com/albums/nn204/jayinbarrie/SuziCan09/?action=view¤t=DSC02448.jpgI did a 3" body lift with square tubing. With all that space I HAD to lift the tank.
Cousin had made up a solid rear bumper out of square tubing. So I was not worried about loosing rigidity for the frame.
I cut the two brackets above the tank. This raised the tank enough that I could put the front lip of the tank on the cross pipe. I put a peice of angle iron across the back tying into the body lift blocks, this supported the rear lip of the tank. The tank is almost level, has a slight tilt forward. There was a 'bump' under the body on the driver side that I had to pound back to fit the tank nicely.
I would guess a 2" body lift would let you support the front of the tank just below the tube cross peice. Even without a body lift you would gain at least an inch, plus it looks so nice when you have a better view of your rear axle.
I recently got another '99 Tracker. Plan to stay away from a body lift this time, but still may do the tank lift. Good way to keep the fuel safe and the trail clean.
Inbetween all pottental rub points I did put a thin rubber mat. The tank just fits between the frame rails.
Would be a good time to do a rear bumper. If you grind out the openin of the frame rails 1x2 square tubing fits in tight (there is a indent in the frame, but you can get it in 8-10" I think).