A loss of compression is not uncommon after a hard run like that, 9 oz of fuel at full bore on a stand is a little harder than I like to run my engines, but still should not really hurt it if the oil and tune is correct. Which from the sounds of things it was.
I have noticed several times right after a landing the comp is down, but 5 mins later it's back up where it needs to be.
I wouldn't worry about it and fly it, sounds very normal to me.