How do you feel about Liquid and its opreturns for peg ins?
nostr:nevent1qqsf40vga9ezn345ynrmtnkq4cmy2rfwkd6cruumqp5c3eup9e8vhhqppamhxue69uhkummnw3ezumt0d5q3gamnwvaz7tmjv4kxz7fwv3sk6atn9e5k7qg5waehxw...
I'm not that familiar with Liquid but a 40 byte OP_RETURN sounds fine. That's a standard transaction pre-v30 and would still be valid after BIP-110.
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