How to mount a KAI KRISTIANSEN Wall Unit?  

The distance between the uprights is determined by the width of the pieces that you wish to hang from the uprights. In other words, if your shelves want uprights at 39 9/16 on center, it would be best to install the uprights at that distance.

You might discover that using an actual shelf as a purpose built measuring stick is more effective than using a tape measure.

If you have a stud wall and the studs do not line up with your wall uprights, you may need to visit the hardware store and peruse the wide selection of anchoring products and their various weight ratings. Molly bolts can be effective for high weight ratings, but they are a extremely difficult to position. Perhaps some plastic anchors, and a molly bolt up high to bear the weight.

If you have a 20 inch thick adobe wall that is neither plumb nor flat, and requires 21 inch long through bolts with fender washers countersunk into the opposite wall, I really feel for you.

Or perhaps I don't understand the problem....

From what I have seen of the FM wall units, there is the central oblong hole in the wall standards. This hole seemingly supports a shelf/case-piece from either side. So you want the brackets to be on either the far right or left side of the oblong mounting hole, so that shelves/case-pieces can be next to each other in the same hole. You don't want the brackets centered in the hole. I am not sure what the measurement is off hand, but you can expect that it will be a metric whole number, probably in cm (imperial will just be some messy fraction most likely).

I think your best bet, as Leif described, is to take 2 shelves, and put one at the top of two wall standards and one at the bottom. Ideally these would be the smaller of the two shelf sizes. You will need someone to push outwards, gently on the two wall standards, you can then measure the inside edge, to inside edge distance. This inside edge distance, will help you get the correct spacing on the wall. Conversely, the inside edge of the oblong hole to inside edge of oblong hole, should correspond to the inside edge distance of the brackets on the back of the shelves/case-pieces.

From there it is then a matter of mounting the standards in a vertically straight fashion, and positioning them where you want them. Best to start on one side and work across, testing fitment as you go. If it is any consolation, the Kai K design seems easier to hang than the System Cado, that I just acquired.

As an aside, does anyone know whether FM stands for F

They are also sometimes called "Fornem M

Thanks Dr Poulet, that answers my question. I think I might have transcribed it incorrectly from Fornem M

Well, I guess that is the reason:

The name behind the FM logo was Feldballe M

Thanks Leif, for rounding out my understanding, .... and I dont agree that it "is too much information."

There is rarely such a thing as too much when it comes to topics like these, especially amongst people who with a common interest in them. I find all of it interesting.