Third-pair validation of the pairs-ratio mean-reversion mechanism class — deliberately using BINANCE perps SOLUSDT and ETHUSDT, which the data-infrastructure layer just explicitly confirmed as 'always safe' (verbatim from the system's failure-action message: 'BTCUSDT/ETHUSDT/SOLUSDT.BINANCE on a 1H/4H/1D timeframe is always safe'). The analyst's most recent refined heuristic requires 'replicating positive expectancy on a SECOND instrument with the same implementation' for mechanism-class validation. With ETH/BTC MR on HL (in pipeline V2) and SOL/BTC MR on BINANCE (in pipeline V4) already running, SOL/ETH on BINANCE adds a THIRD distinct pair to the validation stack — different from both because it ranks two top-3 ALTCOINS against each other rather than altcoin-vs-BTC. SOL and ETH have ~75% correlation but distinct narrative drivers: ETH = smart contract platform with DeFi/L2 dominance; SOL = high-throughput L1 with DePIN/memecoin culture. Their ratio mean-reverts over 30-60 day windows as narratives rotate. This hypothesis fills three under-represented portfolio buckets: (a) pairs scope (14.6% → reducing 78.6% single), (b) market-neutral direction (9.3% → reducing 90.7% long-only), (c) third-pair-validation evidence for the pairs-ratio mechanism class. CRITICAL DATA SAFETY: BOTH legs use the EXPLICITLY-SYSTEM-CONFIRMED-SAFE instrument set (SOLUSDT.BINANCE + ETHUSDT.BINANCE) at standard timeframes. NO supplementary data, NO funding rates, NO HL-native bars (which have refill issues), NO BINANCE_CM (just abandoned for missing history), NO BINANCE_SPOT (recent refill issues). This should be the cleanest Layer-3 verification path possible.