Installed without any major difficulty. Would seem to be a wise precaution given the expense of a damaged belt. Some might say this is a lot to pay for a flimsy piece of plastic, but from an engineering perspective, I think it is well suited to the task!
To install, it is best to get the Spyder up on a lift, makes the job go easier. I also recommend peeling back a starter section of liner and taping in place. I did this in two opposing directions, each starting in the middle, and then peeled back each half once the guard was aligned. This 3M double-sided tape is what is used on auto body molding and it really sticks, so you want to be sure the alignment is absolutely correct before adhering; once it is stuck it is there to stay! Based on 3Ms installation procedures, they also advise applying a full 10 seconds of pressure across the taped area for complete adhesion. And definately use the adhesion promoter! One more install tip. The outer belt guard is held on by two (T-30) screws with self-locking 10mm nuts. These two nuts "float" and must be held in place to loosen the screws; the nuts are hard to get to. The two J-nuts provided with the SPY149 are meant to replace these two nuts, making reassembly much easier.
I do think the install instuctions could be improved, but I am a technical writer and even say that about my own documents!