275psi between the 2 regs isn't that bad, but I would raise the Max-Flo's pressure to 600 as the output. That way you don't have to worry about drop off and the secondary reg has enough to work with.
Personally, I used to run a Max-Flo going into a sidewinder for my sto. It was consistant, but there really wasn't any need for a secondary reg, especially after a Max-Flo. I pretty much tried that combo for the same reason, to keep it as consistant as possible. I realized though, that it wasn't necessary to have both. So i just put a gas through grip on and i have my sidewinder sitting in my kit, just in case. Both are excellent regs though.
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