vertical forge build

[firefarm39]

Well, I saw a demo of a vertical forge being used to weld a billet and decided I needed one! I had an old (my first) forge that really was over-size for what I do, but it looks like it might work really well if I just set it on end. This will be a blown propane forge. My plan is to use a couple of pieces of 3"X3" angle iron welded vertically to trap the cylinder but allow it to be lifted up to service the forge, such as re-lining, cleaning out the bottom, etc. The forge was made from the top and bottom sections of a 100 lb propane tank. The pedestal is a cracked rim from a hay wagon, an old worn out disc blade, a piece of pipe and an old bit of 1/4 inch diamond plate. I am wondering a couple of things. First, how large should the openings be into the forge. I have a piece of 4" square tube and a piece of 3". Are those large enough to fit billets for pattern welding? Also, any advice regarding the size of pipe for the air blast? I was thinking 2", then reducing down to 1" to enter the forge. Any input advise and constructive criticism is welcome!