I was able to get the CB250 Nighthawk fender modified over the weekend. It is is a pretty easy fender to adapt.
You need to cut off about 3-1/8" off the fender mount, then weld on a piece of 1" wide steel flat across the bottom. I cut off 3" and the new holes ended up a little closer to the top....so 3-1/8" would work a bit better.
Here is the fender mounted, and I have marked the ends with green tape on the tire so it can be compared to the Kawasaki and stock Savage Fender. The fender doesn't wrap over the sides of the tire much.....it is very similar to what a Sportster fender looks like. There are 2 hole where a rubber cable guide plugs into the fender, and it is too low to be of any use on the Savage (speedo cable on the CB250) - those holes will have to be welded closed.
Here is the Kawasaki fender. It is a bit longer, and it also has more fender wrapping around the side of the tire than the CB250 fender. (It would provide more protection in the rain).
Here is the Savage fender, and the green tape on the tire is the CB250 fender, the blue tape is the Kawasaki fender.