Aero Adz
The spin is the least predictable manoever in any flight test program. This is not the place to experiment with non standard control/power actions. I would suggest that unless you have had comprehensive aerobatic training which should include how to recover from any attitude, and spin type, you should not be exceeding 6 turns flown in accordance with the POH spin entry and recovery procedures and with lots of extra altitude. In any case any indications that the spin is starting to flatten should cause an immediate application of spin recovery control inputs.
Sorry to be rude but if I was the chief flying instructor at the school you worked at, we would have a one way conversation that would indicate any further attempts at playing test pilot would result in your immediate termination.