I use silicone lube to insert the neck into the tank, I push it in just a bit far. Then I raise the tank up, insert a jack and block of wood under the tank to hold it up and hook the straps and j-bolts. Make sure the tank is lined up, tighten the straps and then I pull and twist (if necessary) the filler tube into the opening. I think I have done it without pulling the tank about 30 years ago but I wouldn't recommend it and the damaged grommet is going to happen from over angling it.
Sheldon