Given the numbers from Sandy, which states 60ml per 4x5" you need 240ml per 8x10". While it's quite possible a full litre will be enough for 5 sheets, there is a possibility for failure.
Looking at my own processing regime, I normally use either 1.5 stop minus, normal or 1.5 stops plus to compensate for the various contrast situations out there. (Looking out the window, something tells me that I will have to do a lot of plus developing over the next 5-6 months.

Sweden is very gray during the winter months.) I would guess that the 1000ml of developer would suffice for the minus and normal development, but is it "linear" for the plus development?
While you can (and should) test for the minus and normal times, I recon you can pin-point these times using only one or a few sheets. But finding the plus time is a different story. Here goes (with my estimations from my own lab): A starting time for 1.5 plus development would be e.g. 30% more time. But I will not test this with one sheet and 200ml of developer, as I don't think the drum will react the same with 5 sheets and 1000ml of solution. So you either have to "burn" a few test sheets, or you can develop a few shots which are at least close to perfect (or too soft if the developer doesn't suffice). I don't know if changing the temperature makes anything to the the exhaustion point, but going for 24degC instead of 20 could possibly be a make/brake point.
Or you can make life easy and see to that you use enough developer. That is: go for 1:1:75 or so and make your tests from there. (There are many who uses Pyrocat for e.g. Platinum or Carbon, where higher contrast is needed. They simply use the developer at 1:1:50.)
Last, if you like Pyrocat, there's no need to change developer. Simply adjust.
May I add that Sandy is very, very modest about his creation. In my mind it's a very nice and versatile developer. Hats off for Sandy.
//Björn