I've wondered the same thing as I have some surplus but haven't ha the guts to ask them. But seein as money's tight this week I might just do that next week. Liberty's right -they shouldn't be able to force it unto you.
I informed my pharmacists last week that I didn't need any Sachets this week as I got some off my sister for when she tried LP and she said that is fine so They will not have a problem with you going in just to get weighed, SO GO GET WEIGHED