I own an Ampeg BA-115, and my two rear tuning ports were accidentaly removed about a year ago (the cylindrical cardboard inserts in the back). I noticed it didn't sound as good, so I researched these and found out that they are essential to the amp. So a friend and I found some old cardboard mailing tubes, and cut them to about the same size as the actual tuning ports, sanded them down, and stuck them in. I was wondering if any SLIGHT difference from these ghetto rigged tuning ports will change the sound that the amp would have with the ACTUAL tuning ports. Is it an exact sort of thing where the tuning ports HAVE to be a certain size, or is it just the overall concept of having them?