A couple ideas from the rainy city.
In lieu of the coated straps...it works very well to wrap the frame with a couple layers of old school cotton handlebar tape (Cateye and Velox still make it) then zip tie the struts on. The tape protects the frame... but best allows the ziptie to bite into something and get really tight and never slide.
The other piece of fender gear that makes sliding them into a close tolerances road bike is the Full Wood brand fender reach over kit. This allows you to skip the narrow part of the frame/brakes and continue the fender on the other side.