Shim won't do any good. All it will do is raise the head shell higher. This then requires raising the arm to get back to where the arm is parallel, and you are right back to where you are now.
The way cuing should work, when fully raised the stylus is at least 5 to usually more like 10 mm above a record. Mine looks to be about 7-8mm. When fully lowered onto a record the lift is only about 1mm below the arm tube. This is with the arm tube very nearly parallel.
This does not leave a lot of room for error. The arm can easily be set up a bit too low, creating an angle below parallel that is hard to see, but enough to lose those few mm of extra lift you are looking for.
I would do like I said, raise the arm a bit, listen, raise a bit more. If the arm is too low, VTA too low, the sound will be a bit bloated, fat or smooth. Raising the arm will tighten this up bringing things into focus with more detail. That is, if VTA is indeed too low. The only way to know for sure is to keep raising the arm, a little at a time, until at some point instead of gaining articulate detail you start to lose weight and the sound gets thin. This is how you know you went too far. Back off a tiny amount. At some point you find the right balance of weight and detail.
My guess is more likely you are a few mm too low than the arm lift is defective. This is how you find out.