I've seen a lot in my life time which includes..... yes, sometimes there was a shim used to keep the starter from going so deep. That shim can be bought at the local Advance Auto, Napa and others. If that is what you need.
I have also seen new starters come with a small rod in the box. I think the short rod was 1/8" and was used to stick up in the flywheel to make sure the starter was not to "deep".
Not sure if any of this will help in your case but if its slow to disengage it could be because the starter drive is to deep in the flywheel. This is just information and hoping it may help.
