Yeah those plastic plugs are butt ugly.

Anyone who can answer this question?

It depends how big a gap there is between the plug and your rock. The polyps will stretch and attach to the rockwork, but if it's too far away....I'm not sure. I would try to cut as much of the bottom part of the plug off as possible!

What you could also do is, put the frag on your sand and when the polyps spread to the sand, frag those ones...and then you can place them wherever you want. I'm not sure how well they do on *just* sand, because I've never done it (maybe someone else can chime in!) Live rock rubble would be your best bet.