As far as going from keyword to kanji is concerned, I don't seem to have any difficulty using different "values" for the same primative, e.g. for finger I usually use Shrek but other times just use fingers themselves. No problem so far.

But I've noticed that when I see kanji with them finger primative in my immediate reaction is to think of Shrek. So this can sometimes give me problems remembering the meaning of the kanji where Shrek isn't actually in my image for that character.

Now tending towards being stricter with my primatives so that each primative only has one "value".

I only really have this problem with fingers for its the only primitive that I ever gave multiple values (although this does happen in primitives that were broken up to form a story).

This is partially to blame on Heisig's lack of reprimands: while he more than thoroughly warns readers not to use weak images for person or thread, he does no such thing for fingers, a primitive that is almost just as pervasive and much earlier in the book. If I had known that fingers would have been so common, I would have most definitely assigned it a value much stronger than simply "fingers", but, unfortunately, Heisig did not provide any foresight.