Well the test results are in,...
I just happened to find myself with a hitchhiker on my tramps this weekend (another story) who weighed about the same as me, so I leashed him up and tossed him overboard
We were on a strong starboard tack into 15-20mph winds (in sheltered water). I tied his left wrist to a 9' quick-release stretch leash and the other end to the right rear Aka, (about a foot from the hull). He "bailed" off the windward side and hit the warm Hawaiian water with minimal splash and hysterics. I remained neutral in the seat and did not assist.
The Good News:The boat quickly came from about 6 knots to a slow crawl, and turned gradually into the wind. After turning, with a couple kicks he was aboard. Nothing dramatic. It all took less than 30 seconds.
The Bad News:None really, but I did observe that if you are wearing a VHF radio/sunglasses/hat, you may become preoccupied with saving them and not yourself. Consider the risks here. It will make things harder if your hands are full of any sort of gear (including your precious rod/reel, electronics, etc) that may have washed over without a tether.
Conclusions1. I am confident that in fair seas, the AI will not go far with you attached to just about any point. (I suspect you will have a harder time contending with whatever caused you to take a dunk in the first place- like high waves, collision with a reef/obstruction or an angry bullshark who doesn't like red Hobies).
2. Use a wrist strap or harness. You would not want to be dragged by your feet for any distance. It will impede your swimming and recovery.
3. Unless you are fighting a record fish, let go of everything else but your lifeline!
4. The boat should slow within a few seconds, but can still pull you along slowly until it turns into the wind. Making yourself "larger" will increase drag and should help to stall and turn it. THIS is your chance to get back onboard before it shoots off in a new direction.
5. A long leash is not necessary. Shorter may be better
The ocean is unpredictable, but after this quick test, I feel confident that a leash will work and is far more likely to save me, than kill me.
I look forward to Maui Bob conducting tests with his TI. With its faster hull and BIG sail, that would be a whole other rodeo ride! (Good luck finding a crash test dummy for that one, Bob).
PS. If you don't have access to tramps and a human guinea pig, you can simulate the same test with a couple sandbags, wrapped in a PFD.