Impossible to answer question.
Each engine will exhibit it's own peculiar charastics pertaining to timing and timing changes.
Some are extremely timing critical and others are not. An example is one I tested not too long ago that was set at 31 deg in the initial testings. After we got some color in the plugs with numerous jetting changes we bumped the timing up by 3 degreees and lost considerable hp and torque. We moved it down by two deg and it came alive with the best nubers in all rpms. We moved it down two deg and lost much power in hp and in torque. REsult is that it wantted what it wanted and even two degrees ruined it either direction. On the other hand I have seen engines that respond sloyly to timing changes and even a 4 to 6 degree difference doesn't change things a bunch.
My suggestion is the same others said. Get the motor to where it is happy and by electronic retards only retard it when using nitrous.
Ed