I got those hard panniers you mentioned mate. Got them for a 2500-mile trip around Europe. They performed very well indeed, although the rubber seal around the inside tore - must have been due to the constant packing and unpacking.
Mounting them was easy enough. The only hitch was that the brackets aren't designed to be used together with the sissy bar mounting brackets. Not a big problem though, I just used M8 washers to sit in the hole in the sissy bar brackets, and give a flush surface on which to mount the pannier brackets. Once they were on they were solid enough.
I would say that a drop of threadlock on the screws that mount the brackets to the panniers would not have gone amiss, there were a couple of occasions where I had to tighten them on the trip.
Overall though, I was very pleased with them. Rode through a couple of very heavy rainstorms, and all my stuff inside was kept nice & dry!!
HTH :-D