20 to 25lbs is the usual size plow/spade type anchor. With Fortress FX 11 is what I choose for bow, and FX7 for stern. I would never have only one anchor on a boat. Most of my C Dorys I had a plow or spade for the primary, and had at least 2 fortress anchors for stern. (When going stern to the beach in an area without tides, for example lakes, a bow anchor is set off the bow, and then two stern anchors about 45* off fore and aft axis of the boat are set on the shore, usual in the sand.
Far more important is the anchor design, For many years, the only anchor I had on racing sailboat was a High test Danforth. I carried a genuine CQR on one of my combination racing and cruising boats 35' long. The 62' full keel ketch we took Long Beach to the Med and Baltic and back we had primary of a 70# CQR, a back up 70# CQR, one 70# Danforth HT, a 20# Danforth HT and a 12# Danforth HT. A 70# purpose built fisherman, and a 150# 3 piece fisherman as a storm anchor. I drug a couple times--one was "Cobble stones" and one in soft mud, twice the CQR was fouled. Ie: the point was fouled by a quart Mason jar in a CQR. Dragging 4x in about 1000 nights of anchoring is an acceptable number. We had one Danforth, one CQR and the smaller Fisherman on rollers off the bow sprit.
I had the same assortment, plus a 35# SS Northhill pattern (PBY seaplane anchor), and the CQR were 60#. the Danforth was 40# on. our Cal 46. We had over 600 nights at anchor with that set up and drug once, in cobblestones.
The best bow anchors today are 3rd generation, like the Manson Supreme, Sarca, Ronca, spade, mantas etc. The Fortress has taken the place of the HT Danforth.
Many of my boats came with a Delta, and it is slightly better than the CQR.
If buying a new anchor for a Cory 25/26 I probably would go with a Mantus 25, a Fortress Fx 11 and at least one Fx 7. If the boat came with a Delta 22, I would keep it and buy a Fx 11. Of course where you anchor has some input. With a trailerable boat, you may easily use almost every type of sea bed.
I purposefully left out the "Bruce" copies. I have done some testing with one and it did not come out as well as many of other 2nd or 3rd generation anchors. I realize that some in the PNW feel it is an excellent anchor.