Use the yellow polypropylene
We have a 40 foot Hunter and used to do a lot of this type of anchoring when we were in the NW. We didn't need to in the San Juans, but did use the technique in Desolation Sound and The Gulf Islands.Polypropylene line floats, which makes it difficult to get caught in your prop. Also, hauling wet soggy nylon anchor rode in a dinghy gets to be a bother. We also found that most people using this anchoring method, use the yellow line.For your size boat, 1/2" would be just fine. Roll it up on a spool and you can get away with quite a bit of line. When setting the stern line, run it to a tree with your dinghy, then bring it back to your boat. That way, you can get under way without leaving your boat. We had 200 feet of the stuff and if we couldn't be within 100 feet of shore, we would just tie it off to the tree. Butmost of the time, our stern was about 50 feet or so from land. Just make sure to check the tides a lot.