Help! Is there some way to anchor a fiberglass sink other than caulk? We have an "offset plumbing issue that involves floor joists. If we connect our drain pipe, it pulls our fiberglass sink. Really missing the metal clips used with the stainless steel sink.

So you are changing the sink's style and are trying to do so without changing the drains? Your only real solution is to caulk the sink down, and move the drains to where they need to be. If a floor joist is in the way, you can go around it. If you think this project is over your head, call in a pro before you try to 'make it work'. Box stores can claim that you can do it, but they don't really help when you need it.

If you apply good quality silicon to clean surfaces and let it dry for a day, it's not going to move w/o some concerted effort.

As to the 'offset' issue, a good plumber should be able to find a work-around for it. Post some pictures and we might be able to offer suggestions. The drain shouldn't have to be forced into position.

IF connecting the drain, moves the sink, then you need to revise the drain line.

Exactly.