I just saw an adjustable track bar on a 2.5" ome lift with the n66 shocks, no bumpstop extensions, stock control arms, correct pinion angle, d30 stock diff cover, and centered axle not hit the trackbar on the diff cover. Im fairly certain it went to full bump with both front tires at the same time too, Theres not a hint of any contact on the diff cover, axle where bushing might hit, or the track bar.
It's a jks adjustable track bar, and it appears to be bent foreward to where it has plenty of clearance from the diff under full bump. I saw other pictures of the same or similar jks trackbar hitting in this thread, but this one doesnt. This leads me to either one of the two following conclusions reguarding the jks trackbars that were shown hitting in this thread. Either A: the suspension in the pictures with the trackbars hitting wasnt aligned properly, this particular rigs mounts might have been off from the factory (I have heard of jeep not being precise with the placement of mounts when building) or a combination of both.
So sounds like there is definatly hope for an adjustable track bar that works for under 3" of lift.