We have a relatively new Drake, 1.28 gal, model ST743 E. Got it here. Sure wish we could increase the amount of water flushed from the tank. Is there any adjustment capability? And what is that black float above the flapper for?

If no adjustment capability, can the fill valve and flapper be changed out to attain a 1.6 gal flush? I think that is what I really want to achieve.