Hi Toby, the anchor that came with our Parker 2520 was the Lewmar Delta 14 lb. (supposedly a 'match-up' with the Lewmar windlass). I am the 2nd owner of the boat; the 1st owner mentioned that this is what came with the boat. One of the first things I did when I bought the boat was 'toss' the 14, and put a 22 Lb Lewmar Delta in its place.... I had NO previous experience with a Delta anchor (My previous 'go-to' anchors were 35-40 lb CQR's, Bruce and Fortress anchors; all much 'over-sized' for our boats as we were cruisers who spent countless nights 'on the hook'...Bigger-Better! ☺....
So far, the Lewmar/Delta 22 has been OK; it has held in severe conditions... As had been mentioned by many Classic Parker guru's, the amount of chain is equally important. These Are "Burying" anchors. They MUST be buried in the sea-bed to work well, and long heavy chain helps make that happen...
EDIT; your local conditions/sea bed, plays an important role in how well the anchor holds; (sea bed?; hard sand? soft sand? hard mud? soft mud? muck? rock? etc.... No one anchor works great in all conditions. In eastern NC we have virtually NO rocks (rocks are 'imported'; we have to BUY rocks!!; where I came from, of you wanted rocks, you pulled your pick-up truck to the side of the road, and fill it with rocks! ☺)...
The 22 lb Delta has been OK for our hard and soft sand, and in our mud in eastern NC; again, the key is to bury it, and that is where chain helps.... Then there is the added; How much scope to use? For day-time/'lunch-hook' under moderate conditions, I use a minimum of 5:1. (Remember to Add the Distance from the bow-roller to the water, to the water-depth, to get the correct ratio).
But I prefer at least 7:1 (If there is enough 'swinging room', the more the merrier). For over-night I have always used a minimum of 10:1 as long as there is room in the anchorage.... For over-night, if expecting strong storms, I have used 12:1 !... I KNOW! I have, many times been accused of 'over-kill'... so be it; I sleep better.....