RE: does changing oil mix change tune on DA-50?
I don't know if Bel Ray's HR-1 and MC-1 behaves the same way, but my take on using MC-1 at 50:1 is that if it's not burning then it's lubricating and cooling the engine, and I sure don't mind losing the odd minute or two of flying time per tankful in exchange for a no carbon situation.
Karol