So if I do some mental math, to counteract the sell pressure of HIVE to obtain HBD, I say drop the rate of HBD to 7.5%

There is no such pressure though. No one is buying HBD for savings at the moment. And obviously such talk is pushing people away from savings more and more. HBD savings went down by a whopping 1M HBD in the past 6 months. People are exiting HBD savings. And you are proposing that we should pour gasoline on this process.

On the more point, HBD is locked up Hive. Hive removed from circulation. Giving away 20% APR when Hive was at $1 was the problem. We lost a tool that we could have used today to relieve the sell pressure. When we should kept it in our bank and increased the HBD APR now to get Hive to HBD.

Mechanism is simple, when price is low have high APR on HBD. So more Hive gets converted to 1 unit of HBD. When price is high reduce the APR, so that 1 unit of HBD gets converted to less Hive than originally put in.

HBD savings have not been the problem. Problem have been non-sensical DHF funding, and bad curation. Giving millions of Hive to people that does not want to be stakeholders.