I'm currently running 235/75/15 tires (on 15 inch black steel wheels w/spacers) with Jeff's 2" coil spacer lift on my 03 2-door tracker (no rub).  I'm wondering...can I go slightly larger to 30x9.5.15s without adding more lift, or am I likely going to have lots of rub?  Does anybody have any experience with this setup? 

You should be able to.  To get a better idea you should have someone slowly turn the steering wheel from lock to lock and watch the tire to see where it comes closest to the inner fender.  Next turn the wheel to full lock and check the clearance between the tire and the frame.  But my guess is that with the wheel spacers you won't have any issues with frame rub.  And fender clearance is only a BFH away.

Typically, 30" tires are seldom a full inch larger than standard 235 series tires.  You are probably gaining half inch. In additional tire diameter... So it should not be an issue.  The difference between 235 BFG A/Ts and 30" BFGs was less than an inch.

Thanks for the help!

-Dan