I have used a shim to adjust the neck angle a couple of times. I just put in a small strip of veneer in the back of the neck pocket. It's a matter of trying what the thickness of the veneer must be to get the desired neck angle. Always worked for me.

I’ve done similar to Marcel.

For the shim material, I’ve used old business cards - which are thicker than the 0.6mm veneers - when I’ve needed a large angle, or a couple of pieces of veneer stacked on top of each other.

Cut one veneer to - say - 2/3rds of the length of the pocket, and the second one to half that length.  
I’ve not encountered a problem with the screw holes then being slightly out of alignment.

thanks, I’ll have a go at making some first but at least those are a sensibly priced option

@tej No probs. When I spotted these, I thought of you. Knowledge is power. 👍

G&W are selling shims now too. 

@boo thanks, I’ll have a go at making some first but at least those are a sensibly priced option

But these shims are flat, so they don't change the neck angle. So if you want to change the neck angle you have to sand a taper on the shim before using it.

@marcel Yeah, I used the link to that page because it was the first one I landed on, if you look further on the website, I’m sure there will be angled ones. 👍 I was just informing you of a company that is selling them that isn’t StewMac. 👍

https://guitarsandwoods.com/g-and-w-neck-shims-for-s-and-t-style.html 

People don’t say that to me very often

Ive made a very rough sketch of how I would estimate the finished taper in wood.

@rocknroller912 Thanks for that, makes perfect sense 🙂