Before revision:  We also prove that Martingale Fishmonger has   an MVP of around 1.63 , and conjecture this to be an information-theoretic lower bound on the problem, independent of update time.
After revision:  We also prove that Martingale Fishmonger has in particular is optimal among linearizable sketches, with an MVP of around 1.63 , and conjecture this to be an information-theoretic lower bound on the problem, independent of update time.