I think you will find that distance from center of the sideplate will have a huge effect. If you have no shelf and are shooting off your thumb, you will need a really weak spined arrow. If you get a cut closer to center with a shelf, the spine will need to be a bit stiffer.
I'm currently shooting some full length (30") CE 75s which are spined around .670 with 145gr points out of a 46# longbow and .600 spine GT1535s out of most of the rest of my bows with 175gr points. All of these bows are cut very close to center. If I go up to .500 spine 3555s @ 30", I need at least 200gr up front.