The tide left me a tiny bit of soft sand to run on, which I did for 35 minutes at an average heartrate of 140. I think I now found the right arm that the watch likes to be worn on and this time I had no issues. I am actually impressed with the optical heartrate accuracy and happy that I am now strap and bug free!
I am also thinking about moving towards the 80/20 running, as this seems to somehow occur naturally with me. I do plan on keeping the easy days easy and continue with hills on the longer and medium days, but if I do feel really good, have no stress due to my business, got my fuel sorted, I want to speed up and play a bit from time to time. As long as I keep my resting heartrate and MAF pace in sight I should be ok … or learn from any mistakes.