NOTE - after several very rough off-road rides, underside of the OS-Base is showing light signs of wear where it contacts top side of the Luggage rack. Other problematic spot is where straps fold over the rack. It's a good idea to protect both the underside of the OS-Base and the straps with some duct tape. Other solution is to move the entire OS-Base further forward so it doesn't make contact with Luggage rack.
Fuel cap is easily accessible which is rather welcomed feature.
Lower straps are conveniently attached to Heel guards. This way, the entire OS-base can be installed or removed in no time.
Comparing Standard and dedicated 690 OS-base, there are several noticeable differences. Angle of the new base is better matched with the angle of 690's rear end. New OS-Base has straps at each corner, while the Standard base has only one strap.
These two improvements give more stability to the entire setup. Not that this was ever an issue with the Standard OS-Base, but OS-18 bags sit better with the dedicated 690 OS-Base.
Kriega OS-18 Adventure Pack is a very good choice when it comes to KTM 690 luggage. Bags have enough capacity, even for a longer trips. Being waterproof is always a nice feature to have. Fit on the bike is excellent. There is no noticeable bounce while riding even the bumpiest of trails. LHS is not touching the silencer, but it's still advisable to use a heat shield.
Luggage rack remains free and it's possible to mount additional luggage. From my experience, smaller capacity bags, up to 20 liters, work best.
Kriega 690 OS-Base with Perun moto Extension plate
Adding Perun moto Extension plate for KTM 690 Luggage rack improves usability of the whole setup. The Extension plate has pre-drilled holes for Kriega OS-rack loops. These can now be installed on the underside. By using a countersunk M6 bolts to secure OS-Rack loops, top surface of the Extension plate remains flat. This way, there's no danger of damaging the tail bag.
Keep in mind that G-hooks might rub against the Luggage rack. This will, over time, wear trough the powder coating. Only a minor cosmetic issue which will not influence performance or reliability.
To prevent OS-Rack loops from coming undone, it's a good idea to add an M6 flat washer and a safety nut on the underside. Using a dab of thread locker is also a good option, especially if this is going to be a permanent setup.