You can run one iphone at a time and lap the duo. 64gb iphone SE is going for $140 at best buy right now. I could tape up 10 of them into a jacobs ladder then I'd have 640gb of storage and maybe 10x the battery life of the duo, and money to spare for future expansion iphones.
You could tape 10 Ford Fiestas together but it doesn't mean it laps a Mustang it means you were fine with what the Fiesta could do which, honestly, most people probably (very reasonably) are.