Why anyone would run a sea anchor rode through a block is beyond me. Perhaps there's some deployment issue I'm not aware of. What I have done to eliminate chafe at chocks and such is eliminate them entirely. Instead I made really beefy bowsprit shroud chainplates with an extra hole for a shackle. I have a spliced bridle that ends in stainless steel Wichard carabiners, and these clip to shackles in the extra chainplate holes. The bridle can be attached to whatever rode is deployed, be it sea anchor, anchor or mooring, and there is nowhere for anything to chafe. It takes some fooling around to find all the proper sized hardware, but it was worth it to rid myself of some major chafe sources. And all my several components are modular, thus can be changed out easily as their useful life ends.
If you're not willing to fool about with your bobstay chainplates, a big padeye bolted to the outside of the bulwark ought to to the trick.
If that was confusing, email me (
zenithdistance@yahoo.com ) and I can shoot you a photo.
Best,
Ben