I like the mushroom for muddy lakes and rivers. Never had a problem with the 15# anchor holding my boat. I used a danforth anchor while in florida on a rental boat. It worked awesome, but I think it is meant for sand, so it might not work as well for what you want. I use the anchor I posted before with a 100 ft rope and it works just fine except one lake where it isnt long enough.
The anchor is vinyl coated, and it sits on the rope bundled up under it in that compartment, it never touches the fiberglass. Worked fine for me so far.