Alright, so I did a whole lot of messin' around tonight. Here's the update:
Pulled the partial mold out. Crappy picture, sorry:
I HATE fiberglass dust. it makes you itch, it clogs your nose, makes your eyes scratchy... etc... so I usually gear up like this when I'm going to generate a lot of it by cutting it with an angle grinder:
All trimmed up, another crappy picture...
http://i91.photobucket.com/albums/k281/vermeuliscious/FGBG/DSC02616.jpg
Re-fit into the tank with the tape removed, etc, to check all the edges and stuff:
http://i91.photobucket.com/albums/k281/vermeuliscious/FGBG/DSC02616.jpg
Added a couple of braces, because despite the fact that I did 4 layers, it's still wobbly. I didn't want to make my front shell part, attach it to the back part and then have it not fit because it warped or something:
Here's a sketch of what I've got in my head:
You can see I'm approaching the other side of the tank a bit differently: live and learn! I used 3/4 pine plywood for the long flat parts, so it won't be as bendy when I remove it. This is also much faster... and plywood is cheaper than FG.
While that cured, I sawed off a piece of styrofoam to play with and try to get the hang of shaping:
I carefully heated parts of it with a torch to get this lava-rock like texture, and then misted it with black barbeque paint. I'm pretty happy with the outcome! I wish there was a good way to capture this texture and then melt out the foam, but I don't think it's going to work out that way. Oh well, it'll look good with concrete and epoxy, too.
Everything in the tank:
I stacked up some styro blocks and used some expanding foam on the RHS... I would have thought the expanding foam would go a LOT further... the stupid can is still half full, it's just out of propellant

. Oh well, it's all I need fo rthat side, I can accomlish the rest by stretching fabric/tape, and glueing in small chunks here and there.
Aaaand I'm spent. My 2 800gph pumps arrived tonight, so I think I might spend some time figuring out htf I'm going to build my sump, and work on that a bit tomorrow. I'd really like to get the background to a good stopping point though, so I can finish up getting the tank ready for the glass... it ought to be here any day now and I really don't want a 100lb chunk of glass kicking around my disaster of a shop.