With a 1/2" powder slide you would need a hole size of 0.487" to drop 23.5 grains of Win 296. While that is possible with a 1/2" powder slide, I may not be able to get there with the ones that I offer. The 1/2" powder slides that I sell have a bushing in a 1/2" hole. The bushing would have a wall thickness of and the 0.013". I could probably do it, but that's getting pretty thin. The slide without a bushing (1/2" hole) would drop 24.75 grains of Win 296.
If you find a 1/2" or 5/8" powder slide marked for 20.5 grains of 2400, it should give you 23.5 grains of Win 296.
I'll send a PM with details on how to contact me about the other items if you need them.
Bruce