I work (at least I did, I'm switching job Monday...) for a wheel weight manufacturer. The reality we see is that wheels from different OEM and after market are not closely following the standards, and that's when standards are available at all. The name of the game is to find the wheel weight that most closely match the wheel flange or, if you are a big enough client, we design a new wheel weight to your specs. Trust me, we would LOVE to have the wheel follow strict standards. It would make our job so much easier.
Obviously, I cannot simply post the SAE spec on here but I can tell you that it does contain the recommended detailed width, thickness, radius, etc of some flange types (P, C, T & MC, as mentioned in my previous posts) as well as the recommended wheel weight dimensions (gap, radius, etc).
Alternatively, if you want to PM me I could open a channel of communication with my colleagues and see if you would like to work directly with them to find out the proper dimension for the wheel weight flange.