I certainly am not having "fun at your expense". I don't know your skills or capabilities and can only respond to your questions as I am able to perceive your knowledge in cannon construction by what you type.
You say you have the skills and capability to build, great. We can help you get the knowledge. You started the knowledge process by asking questions.
I still say this a fairly simple gun to build as long as you have equipment big enough to do the work. I am in the process of gathering together the materials to build a bowling ball mortar myself. I am not going to use a pressure tank. You can follow my progress on that build by following the this link
DD's Winter 2011- 2012 project- Ideas That project is still in the acquisition and transportation stage. I still need a piece of 9 inch RS. And, I need to get the steel from California to Montana.
I am in the same boat you are. I have the skills and abilities. I don't have the equipment. I am going to have to farm this work out. I have the knowledge to design the gun. But I can assure you I will be right here asking question if I run on to a problem.
Glad to hear you touched base with Ed. He has a good reputation here and you should be happy with his help.
The Florida mortar is a very poor design. Not only is the powder chamber poorly place but the carriage design is so bad the mortar flips on its back when fired. Each problem can easily be over come.
A better way to build this, would be to weld the powder chamber to the trunnion bar and then slip the tank over the powder chamber, down to the trunnion and weld the tank to the trunnion. Then run a vent liner from tank to powder chamber. The Florida mortar has the tank welded to the mouth of the powder chamber. The weld would be subject directly to the blast and contamination from the effects of that.
The base-flip issue is even easier to solve. Simply by moving the trunnions position at or very near the centerline of the carriage and the flip problem is reduced or removed.