I did a similar thing for the european cup final and it was a very similar figure. However I changed it a bit and compared it with a league game that night, a Wigan vs Leeds game. The ball was in play 37 mins in union and 49.49 in league. Not a lot of diff you'd think, you'd be wrong.
It was 37 minutes out of 90 including stopages but time took off for tries, but 49.49 out of 69 if you took off the time for conversions. or 35% to 70) pretty much double.