Here's mine in its current state:
I used a piece of 4" PVC for the main tube screwed to a piece of sintra. 3 soda cans make up each tank on the sides. The outer shell was made from 2 "For Sale" signs and some thinner styrene I bought at the hobby shop. I used styrene house-siding foam to build up areas and covered it with styrene sheets. This foam was also ribbed inside to make the flare in the back. Lot's of bondo and sanding have gotten me this far...
Rocket Detail
The grapples are aluminum, but everything else is plastic or PVC. I used PVC reducers to join the rocket to the pack. The end of the rocket is a 3"to 1" reducer and the top of the pack is a 3" to 2" reducer. That way the rocket is a tension fit and so it is removable. Tip is the old "resin pull of a drinking fountain paper cup".
My beacon is a mag light and hair spray cap. It slips down in a hole in the pack, and all I have to do is turn it to make the light come on. The tops of the soda cans were some stick-on, push-on lights I got at Dollar tree cut to fit. Piano keys are hand cut (ouch my thumb!) pieces of sintra.
Powerade caps for the bottom of the soda cans.
Comments and questions welcome.