Hello All,
Just would like to pass on some advice if you are looking at doing the bearing mod to the cush drive, from a bad & expensive experience on the weekend that destroyed my swing arm & hub after the alloy casting broke away allowing the hub to move to the outside chewing into the swing arm & hub.
My bike had the double bearing mod (2 x 6304 2rs) that machines 15 mm out of you hub & 15 mm off the spacer leaving a small amount of alloy that stops the hub moving sideways. the better way to go may have been to use the wide alternative of the same bearing (62304-2RS) & machine out only 6mm giving a lot more support. another alternative may be to install a internal retainer clip to take some of the load if there is enough room, I have not had a chance to look at it yet but will keep up to date with how I go.
This did happen while riding in steep country with other bikes, lots of erosion mounds, and going hard with good traction, I have tried to attach some photos but no luck as yet ??

Yes, It is looking expensive and am trying to source a used swing arm, The double row SKF 22.2mm wide bearing looks to be the best option as you are very correct that there is not a lot of the body left to retain the bearings.
I was very careful when seating the bearings & not driving them home too
hard & the machining was checked both ways as to not take too much out.
I also cross referenced it before & after the mod to check for myself that the overall width had not changed.
All I can put it down to is having really good traction, damp rocky loamy ground, steep smooth hills for a long period, lots of erosion mounds, a KTM 525 just in front of me, landing off the erosion mounds then powering on hard with the wheel getting driven into the ground hard getting maximum traction & little slip in second - third gear putting huge loads on the hub.
The hub had near no play in the rubbers as I checked it the day prior riding in the Snowy Mountains, I will get it apart again shortly & add some more photos, The 2 photos that I put on in the first note are when I got home after recovering the bike & putting the wheel & hub back in the correct position. All I can say is if you have the double mod done is to keep an eye on it especially the alloy casting inside the hub for any signs of cracking off the retaining section that is about 2.5mm thick approx.
All I hope is that I can help in that we can all learn from my misfortune.

Mt03
 

Hi as the MT03 Cush drive rubbers are the same and they go at 4000 miles as well just had to gets set of OEM rubbers for the wife's mt03 I would want a set. I have the polly ones in my xt660x from South Africa I put the in 3 weeks ago. I got them off the lad if bought the bike off. He said he paid �60 for them. Delivered.

I havent Dropped off the radar and still supply PU Cushdrive rubbers across the globe , mainly to the Uk, AUs, and Nz

I initially posted the complete rear bearing modification and PU Rubbers conversion here on XT660.com a good few years ago.
I have owned 1 x XT660R and 3 x XT660Z Teneres, my current tenere has 55 000km on the ODO.
Look forward to keep supplying the PU Rubbers