My leblanc model 120 springs do hold the pads open when laid upon its side. But barely. When held upright the pads move very responsively. They close easily they open as I lift my fingers. I can hit the low Bb like a charm and as you stated altismo pops right out. For the record, I am using a Dukoff L7 with a vandoren 2.5. Also my horn looks like it was seldom played before I got my hands on it.