Hello Eddieb. I did this mod to my DR650 about 18 months ago and although it is good I am not sure I would bother again.
I used a supermotard disk kit that allowed me to use the 250 wheel and a 320mm disk and caliper reloating bracket. There are issues with the "floating disk button" circlips not being suitable for highway use and I overcame this by making cupped aluminium washers and countersunk screws to guarantee that the circlips could not come loose.
The other thing I did (that may not have been necessary) was to machine the mudguard lugs off the bottom of the triple clamp and redrill and tap the mudguard mounting holes so the guard is 15mm higher than standard. I did this because the 250 forks have 20mm more travel than the 650 forks and I did not want the tyre to jam under the guard on full compression when using a full knobby tyre. It was not very difficult to mount the steering stem in my lathe and do the machining so I did it just to be sure.
Happy to compare notes on what you did and how well it works. I had my forks resprung and revalved to suit and it definitley is better than stock forks but now that I have done it I would recommend people just use gold valves, 10 weight oil and correct weight springs to suit their riding. I did 7000 kilometres with well set up standard forks like this before doing the 250 fork mod so I have a good comparison.