With that chain, which I think is fine, I try to set the anchor initially with a 2:1 scope (real, from your fore deck to the bottom).
The "too much" chain issue with the shank down is an interesting observation -- I'm not sure I agree once it set, but I've found that trying an initial set with not so much scope out is better for a variety of reasons. Those include the bigger pain to reset so much scope that you have to pull in (with it's mud, clay, or whaterver); and, I think the initial dig into the bottom works at about 2: or 3:1. After you've got it "hooked" or "buried a bit", you can really bury the anchor.
Long ago, we had a Pearson 35 (center boarder) and used to enjoy that creek near the Inn at Perry Cabin (before Lord Ashley turned into an high-end retreat/resort). That Creek has VERY, VERY, SOFT MUD. I've seen a lot of people that found that Creek to be a challenge to get holding in.