What's really important…
The weight of your anchor is not really as important as the pull that will be exerted against it, when determining the size of a sentinnel.Your boat's displacement/windage and the anchorage's wind and current will be the deciding factors. All you can do is experiment and observe.After sending the sentinel about 2/3 the way down your anchor rode, check to see if you have created a signifncant cantenary (angle) in the rode, and have flattened the angle of pull on the anchor. If not, you need more weight to overcome your boat's pull against the rode.Hope is Helpful.