It was obvious that the "L" bracket (still available from Draganfly) would be the basis for the system. As I had mentioned, I didn't want to weld or drill the sub-frame, so I settled on the "P" brackets. They're not concours but they are strong and don't mar (?) the new paint on the frame. I've never heard an unkind word regarding them. Maybe that's a testament to human kindness. So next was to mount the panniers themselves.
When I received the panniers from Draganfly, I got a bag of hardware and two panniers. No instructions. I emailed them to get some suggestions as to how to configure the two hangers and the one lock on each pannier. They had none. I didn't see quite how two hangers and one horizontal pin-lock would secure them but I gave it a go. It looked like the panniers could rotate, allowing the lock pins to disengage. I don't think they got the drift of my concern. It worked well for a while, but one fine day over a rough road, I heard an awful scraping noise. I was naturally horrified by the clear image in the mirror of the left pannier sliding down the road behind me.
I see that Draganfly now supplies an optional "pin lock" to avoid this problem. I didn't like that, since it would require two steps to remove the pannier. Depending on how the pin lock is mounted, one might have to remove one's stuff to reach inside to disengage the pin lock. Besides, that was offered well after I found my own solution. My solution is illustrated in the last two pics. I cut a little piece of aluminum angle, drilled it and fastened it to the Draganfly lock mount. The mating piece on the pannier slips between the angle aluminum and the heads of the mounting bolts on the rack. It doesn't look like much but the panniers haven't come off since, in some 10,000 miles. For example, this last Sunday, I hit a HUGE pothole which I fortunately saw ahead of me at the last second. I got up off the seat just in time. Whew! It was wicked. Next thought was "what about the panniers?" Nope. Still there.
One more little item. The lock brackets on the rack that Draganfly supplied came with rubber grommets for the lock pin to pass through. They're excellent --- for a day or two. Then they're somewhere down the road. I got replacements, to no avail. I finally gave up on them and have been using this system without them for a long time now. I guess they were supposed to provide some friction, so as to prevent the lock pin from sliding back out of the bracket.