It seems that the more the bass melodica is played, the more delay there will be as the rubber bladder stretches. A couple of the bigger Suzuki models have a small bladder at the bass end. On one of mine, that was closed off by a previous owner. It doesn’t seem to me to make much difference on that one. But the bass melodicas require the bladder. I think Melodica-Me’s approach is the best alternative, changing the material of the bladder. It would be interesting to experiment with both thinner (or stretchier) rubber and thicker (or less stretchy) rubber.