Kepra, perhaps we're drifting off the subject here, but first of all, the hull speed formula is for displacement hulls. Your AI doesn't have one, so you can take it with a grain of salt. The AI can get up to about 10 or 11 mph (occasionally more) -- way beyond the "hull speed" realm.
If there is no wind or you don't want to sail some days, you can just take the boat out in the "Adventure" mode so you can pedal with your wife anywhere she wants to paddle. That's about as quick and simple as it gets.
I like to strap the small sail alongside sometimes when there is no time for rigging the full AI or the appearance of wind is uncertain. When you want to sail, just plant your mast and slap the sheet on.
This gives you the advantages of both worlds, just not quite the same speed or stability as the AI. Here's what an Adventure mode, furling small sail combo looks like with the sail up (below).
BTW, who says you can't pedal straight upwind with your sail up?
The most important thing is enjoy yourself on the water. With the AI you've got many choices on how to set it up and use it -- it's an amazingly versatile boat!