There seems to be some interest out there on end link mods to fit Citizen divers, so here is how I did mine. First off, I am no jeweler or watch maker so your results may vary, probably for the better.
First the end product. Looks good to my eye, kind of like an SKX007 with some flash and a new engine.
I had a spare Seiko Jubilee from an SKX007 that I wasn't using so I thought I would try it on my new BN0150. The notches on the underside of the end links looked like they were about the proper 1mm offset and might make a good reference point to grind down the sides from 22mm to 20mm wide. Turns out they are pretty close to where you want to grind to make them fit the Citizen 20mm lugs. I toof off the metal nearly to the notches. Using a grinding wheel on a dremel tool, I held up the lugs to the face of the wheel and took off a little bit of metal at a time. It is easy of loose hold of the end links so be careful and work slowly. Also, I took care not to damage the tangs on the underside of the end links. Also worked from the face of the end link to the inside, that way any metal burrs were on the inside and easier to clean off later.
I held the end links like so. Not the best method! The end links vibrated quite a bit and the metal got really hot. Ouch!
The links nearly shot out of my fingers a couple of times. I was smart enough to wear eye protection for this operation, I suggest you do the same when working close to 30,000 rpm rotating tools.
I'll give some suggested improved holding methods later.
Full width 22mm end link in back. See the notches on it? Grind almost till they are gone. Leave a bit of metal and test fit in the lugs before you take off too much. You can take off metal, but it is much harder to put it back.
Narrowed end link is on the right.
Mask the endlinks with tape or you might get stray scratches like these.
Also work slow, the metal will discolor if it gets too hot.
You will need to round off the sharp points to fit the Citizen case to lug curve. I used some sandpaper held along a book edge to gently make the curves. A fair amount of scratching is needed as you can see. You may want to deburr the inside of the end links as well. Fold the sandpaper into a tight roll around a nail or something and work your way from the inside out to remove the burrs from the grinding.
Here is a full width end link sitting on top of an installed narrowed one. See those notches again?
Rounded off the sharp points to fit into the Citizen case to lug curve better.
You may need to bend the tangs on the underside of the end links out just a bit to fit the spring bars. I used Seiko fat bars and a fine point on the spring bar tool to push the pins into place. It is a bit tricky to fit since the BN0150 case has that ledge in there. Make sure the pointed parts of the end link are over that ledge when you fit one end of the spring bar in. The rotate the other end of the pin into position, depress it, and pop it into place.
You're going to need a fine point spring bar tool to get these off again if you don't have drilled lugs. I used Seiko fat bars, but the Citizen spring bars might be easier to work with since they have flanges.
Not a bad fit.
If I were to do it again, I would use a punch to hold the end link, and tape off the face to protect it. A locking needle nose pliers would work but the teeth would need to be ground smooth to protect the end link from damage.
I like the results, the watch and band go good together. What I really like is the comfort. The flexy jubilee conforms well and the offset crown of the watch makes for a comfortable fit. Almost as comfortable as my trusty old 6309.
Hope this is helpful, cheers!