I have a couple sets of dippers and a bunch of home made dippers and customize some, but it's trial and error. To lighten the charge I make the capacity of the dipper smaller (a drop or two of epoxy in the dipper will lighten the charge a grain or two. Shorten the sides of the dipper will also lighten the charge. I glued a BB into the bottom of one dipper to lighten the charge). To increase the charge, just increase dipper capacity; drill or ream interior carefully. Or on dippers made from a case, swage the case (stretch it ) with a tapered punch or the like). Drill (or glue or cut down) then measure with scale. You can get real close to a chosen charge with care...
My Anchor is holding fast!