Xanax is short acting, but it's not really short enough that youd have to redose later on in the trip. Id strongly recommend not using any Benzos except for bad trips, or if you're experimenting with them for information that would help you with using them during a bad trip. Benzos are super addictive, but you probably won't have any problem with them if you only use it as needed for a bad trip, unless you have like 3 or more bad trips a week (which I doubt you do). It takes enourmous doses of Benzos for potential fatality, and with Xanax it's nearly impossible (the lowest potential lethal dose is like 250 mg I think, but I know it's definitely over 200. That's 100 bars). Benzo overdoses only happen when mixed with certain other drugs, but not with normal psychedelics (some disassociatives and borderline hallucinogens like GHB though). Basically, there's no life-threatening limit on the xanax dose. However, it could knock you out for a pretty long time if you take too much, but I mean you really don't have to worry about taking too much here. I'd recommend 4 mg, which is a somewhat high dose (normal recreational doses are about 2 mg), but is still safe and is about what you need to almost garuntee an end to a bad trip. About taking it sublingualy, I'm guessing it would be like 10-15 minutes to fully dissolve. I've never taken Xanax sublingualy, but I've taken lorazepam sublingualy several times, and it took 8-13 minutes. If it takes more time than that, just swallow what's left in your mouth. You could always just pop one of them and take the other sublingualy. Also, crushing it before putting it under your tounge will make it dissolve faster. It dissolves faster if you pretend like you're sucking a straw, but keep your tounge down on top of it so you don't accedently swallow it. Make sure you're hydrated, if your mouth is really dry it'll dissolve a lot slower.