Friction Ring Jib Leads when converting to seat cleats

I am converting from deck turning block and cleats, to the seat mounted cleats for jib trim. Everyone seems to use a 57 or 75 mm block with a long enough shackle attached to the car to get to the 2" maximum from the seat back to the bearing point of the sheave.

Since fairleads and blocks are interchangable in the rules, is it legal to use a friction ring with a loop (like photo attached) or a spliced line onto a friction ring with the tail tied to the jib car for the lead instead of the block & shackle as long as the bearing point on the inside of the friction ring is @2" from the seat back? Reason being friction rings are cheaper than blocks.

And while I'm on friction rings, can one be used on the "Palm Device" for the mainsheet instead of the SS ring?

Thanks

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Comments

Friction ring

I have come across boats that race at various regattas that use the friction rings you mentioned and am looking to do it as well. I'm not aware of any CMR's ruling that they are not allowed.