What gear did you choose for your bridle? What is your boat's displacement?
I have a 16 ft para by Fiorentino Fiorentino ParaAnchor - manufacturers of sea anchors and parachute anchors and storm drogues
to be deployed on a 450 ft 7/8” braided nylon rode. The bridle was supplied by Fiorentino and I can’t remember the size -- probably something on the order of 3/4” braid.
BR displaces 24 tons loaded for sea.
Re. the Coles book and the 28 ft para anchor -- that seems pretty big for a boat that size. I went with Forentino’s recommendation and ended up with a 16 ft anchor for a boat of roughly the same size and 1/2 the displacement. I think that a 28 ft anchor would probably fully stop the boat and in a big blow that means that the rode would take all the strain, much as it would if it were anchored to the sea bed. I think the idea is to have the boat slowly moving backward while maintaining a safe angle of attack to wind/seas. In Coles’ time I think many people used surplus military parachutes for sea anchors and that may be why the boat in question had one of 28ft diameter.
A smaller diameter para anchor should place less strain on the rode and bridle. Also, you can use the anchor with sail up and hove-to. This might also take some strain off the rode/bridle.