Another suggestion, JD - take a small coin, preferably of low value, and glue it to the inside of the base of each Alien figure. Or, use some other item (e.g. a washer). It will add loads of stability to the figure.
I didn't really have issues with the tails...just used Testors model cement and held it for a few seconds, and it worked like a charm. I'd place the figure so that the tail was shored up by something, such as placing it in a box so the tail was up against the wall, or sitting on a pen or something, to help keep it in place while it dried, but the tails weren't nearly the pain in the butt that cutting the tiny pieces of the sprues was.