Its generally recognised that the powder is the first step followed by the distance from the lands.

My advice for a 'short cut' would be to use the OCW method whereby you start with a uniform distance from the lands ( I would suggest 40 thou back) for the weights of powder you have selected when using the 75 gr V max. If you move up in .3 gr increments you should find a node from the OCW target that is good and if you feel there could be improvement then stay with that powder weight but alter the distance from the lands to see if there is a change for the better.