Thanks guys, and any regular thermal fan for a CPU will work just fine?

Is a mixing tube really needed?

Few questions. I recently discovered the BL-520 and it sparked an old flame with cannons I had while I was younger. Questions are as follows: 1. Can I use a centered coaxial barrel and load it in the back still? or will it have to be offset as in the BL-520? For instance, use a reducer/bushing for a...