2 more custom fiberglass box

Two more quick questions before I get started on my project:

1) In the past, I've always mounted my speaker box somehow (i.e. put some brackets in that come up from the floor) so that it is harder to steal and so that it doesn't slide around and is nice and sturdy.  If I make an "odd" shaped box that fits in the very corner of the trunk, I assume I'm going to want to do this as well.  Is this something I need to be concerned about while fiberglassing or when I'm done?  What I mean is, do I have to figure out how I'm going to mount it and then add any brackets and then fiberglass or is that kind of thing best left to the end?

2) Similarily, what about the speaker connections?  Do I leave a hole in the back of the box and fiberglass around it or do I just fiberglass the whole thing and then cut the hole in later?

My current plan (unless it's a really bad idea) is to build two separate enslosures.  One would be on each side of the trunk, in the corner.  Basically, it would be this:

http://mobile.jlaudio.com/products_stealthbox_detail.php?fit_id=1628

However, I don't want to pay $600 for this one, and I want one in each side of the trunk.  Figure I can make a box for each side, buy some subs and an amp for cheaper than the Stealthbox is.  My plan was to make it so I could remove them if necessary, and they would both be above the floor in the trunk.