The next time I take the strings off, I may add another shim. As it is, I think I have a 1/2" block in the pocket! But if all I am going to get is a louder quack from the bridge pickup, I may not bother. The neck sounds really good at a slightly higher string gap. This is why I was thinking it was the pickup's distance from the bridge creating the quack.You should get a lot closer than that. Some of my Gibson pickups have scalloped bobbins from being so close to the strings. No fear of Stratitis with P-90s.
But I am also considering using a different bridge/whammy system which will drop everything down and reduce the neck angle. Just haven't decided which. Gonna live with it for a while and continue ruminating.