Putting the 1.5 mm shim will drop the belt down potentially too low and since there is a lip or protrusion on the sheave where the seal is, it will hit it or will hit it as the belt wears, this is why we machine the lip off with a machined sheave plus you have more RPM throughout the whole range with the shims because you are moving the sheave away from the fixed plate and it will cut down on top speed some to for the same reason.
By machining the sheave in the inside where the weights are you get the same low or actually more and as soon as the belt moves away from the center as you speed up you don't have the lower rpm that the shims would have.
If the lip was not there then a shim mod would not be a bad slow speed only mod.
As far as the weights go, sounds like a good do it yourself job if you don't mind doing all that and have a scale, a melting pot etc where as the slug kits just drop in.
On the purple spring, it is not enough of a change over stock, I would have chosen the gold.
Also, the gasket serves two purposes, one is sealing and one is spacing, using gasket maker could have a potential for concern on the one way bearing that goes between the wet clutch and drum portion.
All in all playing around is the fun part.
You really should not reuse that nut on the wet clutch though. For anyone else wanting to do the lead thing themselves, you can call us, we can sell you gasket, nut and gold spring at a really good price.
Todd