New build question

[Dawg Dude]

Hey all. I'am building a side mount fire box using 2 propane tanks. 100lbs cook chamber 30lbs fire box. I am having trouble figuring out exactly where two make the first cut to nicely fit the two tanks together. Do I cut the cook chamber to fit the fire box? or do cut the fire box to fit the cc? or am I over thinking it. I tried to calculate it on paper but the geometry of joining two convex cylinders of different volumes escapes me. Any thoughts on the topic. (Note tanks are purged and free of any LPG) Thanks

 

[ahumadora]

Pics and some kind of drawing of what you intend to do.