I don't know what would be the right APR, and probably nobody does, we all play the guessing game here, as for the most thing in life :)

But I don't think constantly tinkering parameters is a good thing, and the overall uncertainty that we have with this parameter. Can we try and propose some type of rules and mechanics that will give predictability to the HBD APR and how it is determined, and have this set in code?

At the end the HBD APR is secondary when it comes to the health of HBD and HIVE, the haircut rule is the ultimate protection and the ruler of the system.