8.8cm FlaK 37 mit Behelfslafette

Have not built this kit / brand Colonel,, but it is hard to go wrong with Dragon.

Given Roy's information you would be looking at a base of 13" x  8" or so...   depending on what type of scene you are indenting. You could make the base more rectangular given the length of the gun and cruciform.

Good luck with it

Bill

The cruciform base is roughly 6" x 6".  the barrel will extend maybe 5" from the center.