From everything I have gathered, the additional plenum is of little to no benefit to the power plenum. Now that all comes from here say as I haven't seen anything proven directly. I don't think you can have to much plenum space to hurt anything in this particular gun, but the diminishing returns kick in at some point. Just based on some speeds I have run, I really don't need more on the power side with just having the PP and the slug kit. I am not saying I wouldn't want more, but can break the sound barrier already as is.