I agree that using multiple shims are better then doing nothing.
According to two of the best engine-builders in Germany (HPN and Motoren Israel) this is not good practice.
If the gap is big it’s probably because the canister has moved, and it will probably happen again. When you add shims you increase the risk of a moving canister.
Link from Motoren Israel: http://www.motoren-israel.com/produc...-erneuern.html