I'm looking at doing a 2" spacer lift. While most kits come with bump stop extenders, I'm wondering how necessary these are. I've also read that they aren't required unless you are lifting wheels in tandem off the ground, or dropping whole axles into very deep holes, then dropping the jeep back onto these axles when it follows, and similar beatings. For most normal off-road stuff all they do is restrict the upper travel of the springs. Any one got any experience, or good tech thoughts? I know they are there for a reason - better the bump stop stopping upward axle movement than the body or some other part -  but so are waivers, and warning stickers on windows not to lean out too far if you are above the ground (duh!). Can the old original bumps stops be used, rather than be extended, thus gaining a bit more travel?   

Install the lift without the Bump stops. Wheel the thing if you don't like it  install the bump stops. Building Jeep's is a trial and errior thing.   

error in this case might result in destroyed shocks and wrinckled sheet metal.

If your sticking to tires that would clear before the lift, and your shocks can handle being compressed as far as the OEM shocks or handle bumpstop duty (a very few are made for it), you'll be fine.

what it sounds like you want is to have more uptravel, but figure you don't drive in a manner that it would ever be used.
If thats the case, you'll never touch the bumpstops, so you have nothing to lose by installing them.

Tires are only 31s on a TJ, so clearance won't be a problem. There'll be new Rancho RSX shocks. I'm thinking that if the bumps stops are extended, the bs bottom stays where it is. The tires have an additional 2" of body clearance, but they can't get up there anyway because of the bump stops. As the axle is solid, a wheel on one side can't drop to its max because the spring hits the bump stop on the other side, despite plenty of body clearance. If the bump stop was further up in the spring, then there'd be more articulation (I'm ignoring the sway bar for now).

I'm old school 4WD, which says that wheels on ground = traction, and wheels in air = no traction, and for forward movement you need traction (if you're not flying). So  the articluation to keep wheels on the ground is useful, but the likelihood of bringing the weight of the jeep down hard on the suspension is pretty minimal.

By the way, the main reason for the lift has little to do with the tires; I can't stand the fuel tank hanging like a diaper fill of caca. I'm used to being able to drive over logs, and it's so low when you come off a log it's pretty much sit on the fuel tank than drag off. Every other 4WD and SUV has a better setup than the vehicle that's supposed to be designed for off-road. (Yes, a Kilby tank guard is next.)

I know there are shocks out there rated for 0-2" of lift, not sure if those are them. if you're running a sway bar, you'll be fine. without one, I'd go a little longer than stock, maybe an inch. the added wheel travel should give more flex, maybe enough more to damage something. if you have access to a RTI ramp, a forklift, or something similar, you could double check whats going on.