Bolting Rotopax Pack mount onto Perun moto Add-on plates is easy, since there is enough space to inserts bolts and tighten them up from inside of the add-on plates.
But bolting Pack mount onto luggage rack requires more time. Perun moto KTM 690 Luggage rack SD and most other luggage racks on the market, are made to be low profile. So there is not enough room to insert bolts from below the rack. In order to bolt Pack mount to the rack, bolts holding the rack must be loosened first, so rack can be lifted a bit. That is not difficult nor time demanding, but it can be boring if you do it often.
Fellow rider from US, Bill or AdvMoto18 on Advrider, suggested following solution. Lets call it "Rotopax Pack mount mod". Here it is.
First, remove T-handle from the body of Rotopax mount.
If you check Rotopax mount body, you will find two threaded holes, used for bolting it to the vehicle or onto mounting plate. Those holes are passing through the whole body of the mount. Holes are not threaded all the way, but that is not needed. Thread is imperial one, I am not sure what exact size it is. But it is close to metric M8. Folks from US or UK will know what size is that.
Since I am from Europe, and imperial bolts are hard to find here, I just used standard M8 tap to carve M8x1.25 (standard M8) thread into the holes. There is enough material to do that. If you can find proper imperial grub screws, no need to do that.
Next, you will need two allen grub (set) screws, 40 mm long. A bit longer will do too. These should be found in all better hardware stores. They look like little threaded rods, or headless bolts, but have allen hole on one side. I am not sure about imperial dimensions, but since I carved M8 thread into the Pack mount, I just used metric M8x40 screws.
Now just screw the bolts into the holes, on the bottom part of Rotopax mount. Side with allen socket should go inside.
Make sure you use some threadlocker. I used Loctite 243, so I could remove bolts out of Pack mount some day. But since I like this mod a lot, I will probably apply something stronger, like Loctite 263 or super glue.
Screw the bolts so approx. 24-25 mm is sticking out and leave threadlocker to cure for 24 hours.
Here is what we will get.
Now bolting Rotopax Pack mount to the luggage rack will be much easier. Just position it, center into proper holes, and use washer and safety nut from bellow (for the photo I used standard nut instead of safety nut).
If you used light threadlocker, it may be wise to use allen key from above, to prevent bolts from turning while you bolt nut on.
After Pack mount is secured, just insert T-handle back in, and mount is ready to accept Rotopax can.
Here is how it is on the bike.
Bolting from below will require some practice, and you will need long fingers. But once you get it, it will go fast. Remember to use allen key from above, to prevent grub screws from turning while you bolt the nut onto the screw.
And I strongly suggest using ratcheting wrench for this.