In a Formula Vee, one nozzle is in the cockpit, the other is in the engine bay.
My 5 pound bottle weighs about 7-8 pounds full, and it's rather small. Probably 5 inches in diameter and 12 to 15 inches long. You could easily fit it in that dead space in front of the clamshell latches. Run a pull cable and about 4 feet of aluminum tubing and a nozzle over each carb. Put it on the passenger side.
I made aluminum covers to keep dirt out of that area. A piece of .020" or .030" aluminum 6" x 12" covers one side. Make a paper pattern. I riveted mine in place.