First off thanks for the add. Lots of great info on this site.
I'm no expert on this subject. A couple u tube videos I've watched. ( weights and crankbaits ) explain this.
.25 Oz = 1 ft. A 1oz weight =4ft extra. And so on.
So a 10 12ft. P10. Add 2 oz of weight now gets to 20 ft.
I'm sure speed and line diameter may affect this but I use it as a guide. Easy for me to calculate in my head while 20 other things are going on.
You can check this with you linecounters, depth finder, speed, and weights. Just add weight till your crank hits bottom. 10 ft crank in 20 ft of water. going 1 mph. = ft drop per oz.
Good luck.