I have ran Stabil at a 2X dose and stored for 2 year and 4 months. ZERO problems. I filled the tank until the gas came up in the filler neck to have no vapor space above the gas in the tank. Elimainating the air space will prevent condensation, and keep the gas effectivly "sealed".
Personally, based on my experiences, I would go 3 years with 2.5 X dose of Stabil. If you can't fog, consider a cranking every 3-4 months. Many here will disagree, but I crank my stored cars once every 3-4 months, and let run until hot. This assures new gas (and Stabil) flows into the injectors. Drain old oil at end of storage.