I have cleaned it out (reasonably) well and now the hybrid is screwed to the floor. The barrel is resting on four wood blocks and is fastened with perforated steel band to the floor. The total number of screws that is in the floor to hold it is 16 and they are screwed into an inch thick chipboard.
What concerns me is the recoil it produces and the fact that it is fixated to the floor. I could see roof plates falling off the roof below or the cannon simply tearing itself loose and impacting the wall behind (witch is on second floor, above concrete and it is only 1/2" thick)
I need to sort out if it is okay until tomorrow since I have everything I need to fire it now.
Here is some pictures that is pretty blurry due to the light conditions but you should understand whats up.
Chamber is loose so I can move it to insert ammo and burst disks.

One of the four supports.

Two of the four supports on the middle of the barrel.

I think this is all you need for now.