Width Under Maker-Taker Fee Asymmetry

A maker earns a 0.004 rebate when its passive quote is hit. To flatten, 30% of the time it must immediately cross with a marketable order (paying a 0.006 taker fee); the other 70% of the time it flattens passively for another 0.004 rebate. Ignoring adverse-selection moves, what minimum half-spread keeps expected per-fill PnL non-negative, where per-fill PnL = h + entry_rebate + expected_exit_fee?