I'd set the grommets in first:
Use a cheap string at kind of high on the tension range.
Hit hard against a wall or backboard for a half hour.
Cut out the cheap string.
#1 above, taking your best guess for the new tensions.
MuscleWeave 200G (353g 8.5 HL), Cyberflash 1.25/multi 1.35, @48/53, dropweight stringer