Just my opinion here but the 8mil thick tape is the best compromise between protection and ease of use. Any thicker gets to be more difficult to wrap around the small diameters of most bike frames. I'm making a guess that your wife's tourer has maybe smaller dia. steel tubes. If so I found that with 2" wide tape it covers half the dia. of most main tubes and can be used for stays and such without too much cutting. "Helicopter tape" is just polyurethane tape and as mentioned not all are equal. 3M is possibly the best but I have used another popular brand (of which I can't remember the name of course) that has stayed on my frame for over 7 years now with no peeling or yellowing and also make sure you get the outdoor/UV resistant version. Wetting down your frame with a small amount of highly diluted mild soap or alcohol and water helps to make re positioning the tape easy when applying and helps when trying to smooth the bubbles out and drys completely in less than 24hrs.