Here is my experience with them, not on my Jeep but on a friends.
We spent about an hour getting the lugs ground down enough to be a perfectly smooth area for the GT to adhear too. This was done with a M18 angle grinder. After that, we cleaned the sidewall with alcohol and let it dry. Then GT was applied and the allowed time for drying was done. We aired the tire up. It held until we rolled the tire at which point it started leaking. We decided since the tire had the gash in it, we would drive it out on the flat tire to the trailer for the spare.
I wasn't impressed with them. It may have been the location or the installation. If I were to use one and get it to hold, that tire/wheel would immediately become the spare. I wouldn't trust it on the road at all.