Cornergas great work.
My only concern is your use of net revenue versus cumulative revenue. Reading Spiderman's post, the wording is clearly pointed to cumulative revenue, making the royalty rate increase earlier in the decade.
To play devil's advocate, based on the various cost structures in the oilsands, and assuming net revenue is used, one could postulate that a project may never achieve payout using the net revenue method (simply by increasing operating costs).
I beleive the spirit of the royalty is, we'll give you a break on the project start-up (by charging a minimal rate on the province's oil), but once you've pulled out the equivalent value of project costs, we'd like our fair share.
In addition, Royalties are usually top number based (like revenue), very rarely bottom number based (like net of costs).
Great to see number crunchers on the board.....good luck
Booster