Hog roaster design

Livin'- don't know exactly what to tell you about a design...Have you ever used one?
We have one at work that is basically a very heavy(believe it was probably an underground tank) round fuel tank that is cut in half length wise. The top half was hinged back on with some snow plow springs added on to help with lifting the lid. I had them put an expanded metal along the front and back that will hold about #50 of charcoal total. All of the cooking is done on a peice of stainless that looks similiar to what the military used to use for running vehicles across sand. With charcoal along the sides I don't have as much problem with flare-ups as you would with the fire directly underneath. The whole roaster is just mounted on angle iron legs and takes a fork tractor to move around.
That being said I have also used several other types from an old "flat type" fuel oil tank that was cut in half to another one that was commercially made on a trailer to another one that a friend of mine built from the ground up to look like the Purdue Boilermaker Special. The main thing that all of them could do was roast meat-some of them are just prettier, easier to use or have more bells and whistles.
I guess what I would suggest you do is go around and look at what others have put together or had made for them. Ask them what they would change or what they like about it. Then do what you think is going to work for you. Right now I have a tank and an old trailer that I think could be used for a more mobile unit than what we have at work but I've still got '79 Power Wagon sitting in the polebarn drive that hasn't been touched in over a year so guess what else I probably won't get to for awhile