I will make it big enough (not too big) to add the weight I need. And, like baitjunky said, I can always add lead to the resin pour which will lock the lead in and not react with the plastisol. I like a slow sinker that works like the Osprey Talon. Im using fairly small inserts from Basstackle in a 5oz platic swimbait. It barely gets the baits to swim straight. Too fast and it goes sideways. But it's slow enough to fish deep.
My only question is, will the resin react with the plastisol.
Carolina Mike, thanks for that info. I will definitely look into that coating.