Good morning
First canister of powder I bought when I ETS éd(1973) was Unique. Dad and his Navy buddy used it in 38´s.
You do not want to go Max with Unique. Unique will pressure spike with just a very slight powder addition that pushes it over it´s pressure curve. That is one of the reasons there is such manual variation. Your cylinders are fatter or narrower than mine. Our brass does not expand with an equal ratio. A max load safe in my old Colt Police Positive goes beyond safe in your narrower cylinder and pressure spikes.
Longer cases, thicker cases, fatter bullets, differnt lead hardness, hotter primer, rougher throats.... the variasions are inumerable. But the results are the same when a max load + of Unique pressure spikes. It will ruin a pleasant shooting day.
In my revolvers I shoot 4 grains plinking. 4.5 for serious double tap practice. 5 grains is my never to cross line in 38 Special with a 158-165 grain cast. There are plenty of other powders to use out there that will get +P velocity without pressure spike concerns.