I was going to make a graph of the 2 stroke HFRR at different ratios. From this http://mopar.mopar1973man.com/cummins/general/2-cycle-oil/hfrr/hfrr.htm I know that 2 stroke at 200:1 is HFRR 474 and regular #2 is 636. So I can do some generalizing and figure out a formula by using the 162 difference between the two HFRR's, I can say that 400:1 would have an HFRR with a difference of half that, so 162/2=81, 636-81=555. Now that you know how I have it calculating, I will show you the stats and you can see the issue I run into at the bottom.

I will attempt to recalculate the numbers with the new info of 1280:1 with HFRR of 470, to see what happens and if there is any change.