The right and elegant way to do this is with a press. Whack the axle to length, press on new splines, re-harden and VIOLA, you're back in business! Cutting the axle down and re-welding is actually very difficult, you have to make it strong and straight which is a challenge welding a round solid object. Possible, but definately hard.
But here's another idea that we used with the 901 sideshift transaxle. 901 usings type 1 CV's if you drill/tap for bolt #5 and #6. Now you are using six bolts instead of four. Much better. Most of the flanges already have a hole, just not threads for this. As type 1 axles find their way to many places, there are many lengths available through Swayaway. We ordered a set for ours that are a standard length (for sway-away) and they work great. Swayaway can also make any custom length you need.
angela