My guess is that it is a running change, and would not seem to affect the operation of the top of the sail (locking it in to the top of the mast.
I like to believe that the route I took was easier, just involving finding a PVC pipe joiner of a suitable diameter to fit over the mast (whether or not the top of the sail has circumferential velcro) and securing it with a couple of self tapper screws. Rather than using a rigid bracket, I chose to push the bottom of the wind indicator (Windward brand, a lot cheaper than the ubiquitous Windex brand) into a piece of plastic tube, in the hope that the indicator might survive a brush with low hanging foliage (this has been successfully tested several times!)
I stuffed the bottom half of this plastic tube with some dowling, so the securing nuts and bolts had something firm to lock onto.