Mixing fuel to get 93 octane

[waterboy222]

Oklahoma has dropped 93 octane from the pumps. I can get 86, 88 and 91. And can NEVER find 91 on the water without paying a small fortune for it.
I have about 45 gallons of 110 from Spring and will need to blend my own to get to 93 octane.

But I have a couple of questions. Will 110 and 91 stratify if left sitting for a month or so? Does anyone have an online ration calculator thats easy to use to see how much 110 I need to put into X amount of fuel at X octane to achieve 93?

And do I really even need to worry about getting to 93 or is 91 sufficient for stock 300PM's?

According to my math, for every 10 gal of 87, I will need to add 3.5 gal of 110. Does that sound correct?

I would have to trailer the boat and take it to town to get 91 octane, which would be cheaper in the long run because of having to use LESS of the $9/gal 110 octane.
I could get 100LL for $5.78 at our airport but I'm not sure if you can mix it with 91!

Any advice on getting to 93 from 87 or 91?!