Today I added 400 units at $16.82 mostly.
My cost basis is now $16.83, up from the $16.80 of yesterday.
That said, I don't find myself able to set (in advance of market reality) what my best add-on price/unit might be. Generally I want to be adding when I find I am in position to improve my overall cost basis. Today I back-of-the-napkin style deducted the pending distribution from my buy price and it was to my liking for sure. Obviously if things continue to decay I will be going back to the well for another sip.
I like my present cost basis enough to continue along the same path. And I don't think I could find a more reliable return on my investment.
Good fortune to you!