The best way to mount these is to use some type of rubber padding under the tank so the vibrations from the engine and or flexing from the frams can't transfer into the tank.
I used an old set of gel grips, cut out sections of the grip and then put my tank on and snugged down the bolts, if you tighten the bolts down too much they will stress where they're welded to the bottom of the tank, crack and leak so if you have problems with the nuts working their way loose, use a little bit of blue locktite to keep them in place.
Good sources for rubber under padding for the tank are old grips (especially the gel type) sections of old inner tube, or foam grips, cut a slit down the grip and sit the tank on them, as with all grips, use a section in front, and another in the back of the tank.
The tank only needs to be tight enough to where it won't slip and fall to the side and any type of rubber be it from an innertube or an old grip will further prevent it from slipping so you don't have to tighten the bolts as much.
Also, use the Blue locktite or any other brand thread locker that's light or medium strength, the red locktite grips way too strong and you may twist off the stud trying to remove it later on.