I'd not guess at it. Get the rig on stands, pull the springs & the factory and added bump stops, leave the shocks attached. Slowly raise the axle with two floor jacks until you either run out of shock travel, or something hits the frame, etc. Measure from the upper bum stop tube to the lower bump stop pad. Add 1" (or less, your call) and that's your bump stop length. Ideally you'd do it with the wheels & tires attached, too.
'09 JKRU. 4" Teraflex long arm, Teraflex R44 housing, Teraflex / Fox Resis, Poly Performance skids, Nemesis Billy Rockers, Nemesis flares, 37" ATZ P3s on 17" 5x5.5" Trailready HDs, Spyntec hubs, Teraflex BBK, Mopar BBK master/booster, Superior front & Alloy USA rear axle shafts, CTMs, Reids, Synergy drag link & tie rod, WTOR hydro-boosted steering, 5.38s, TF Dual Rate front bar, TF bumpers, Warn Powerplant, Tom Woods shafts, AA xfer case cable, Kilby canister relo, RH4x4 cage.