Hi aussy,
Thanks for sharing your solution to wobbly wide web access.
Deployment is the issue. If I were going to add a booster I'd want one that could be on the batwing antenna.
I did invest in a high gain omnidirectional antenna which was about four feet long. I used it with a 3 watt external wifi unit called Alpha. I found it useful for extending signals from free sources such as McDonalds. It would give me a useable signal for about 700 meters (765 yards).
Eventually the high gain antenna failed, and by then I had a phone and two cellular dongles to use with a wifi router, so I did not replace the antenna.
I found as time went on that far fewer folks were leaving their connections "open". While it is possible to "crack" the low level codes being used, it is not ethical to do so.