Air cylinder size

I asked this question of one of the air gun retailers and did not get an answer that answers my question.

I recently purchased a used Monsoon that has been fantastic.

I would like to ask about increasing the air cylinder size by either the 45cc extension and the new fill port with gauge, or, a new cylinder, either the 300cc or the 470 cc cylinder.

Would the 300 or the 470 fit the Monsoon or would they be too long?

Is my Monsoon cylinder detachable with or without air? If without, how do I depressurize it without shooting it down?

My barrel with shroud measures 23.75 inches in length and my air cylinder measures 17 inches total length.

Does anyone know what the 300 and the 470 measure in length? And, are the O.D's the same as the Monsoon?