I was thinking about changing the left & right axle saft in my rear sidekick axle. In that way I can manege to offset the diff a little bit wich give me a better angle in the Kicker 3 setup. (Ive calculated that the offset would be +/- 1.5 inch wich is not enough but better as nothing.)

Is that a good idea or not? Has anyone tried somethink like this before?

Sounds like a lot of work for minimal gain. If you're going that far why not just go full floater and alter the tubes to suit the diff position. That way you gain some more strength, could do a rear disc conversion while you're at it and get the diff exactly where you want it. I know it's more work than what you're proposing but the benefits would be 

some earlier jeeps had offset pumpkins, some land rovers too

The reason why i would take this solution in stead of building a full floater is that i want to maintain the stock axle shafts. Here in Belgium it's hard to maintain special costum parts and wenn i would broke an axle it would tike a while before I would get a new one. Or are there easy/cheaps axle shafts that i can use?

The amount of work isn't that much i think: cut off all the brackets, flip the axle and weld them back on it. (And a little arangment with the oil plugs.)

you might get away with using samurai axels, I asked sky mfg. if they would make one for me and they said yes, I could then run 4 door brakes in the back with bigger bearings of the kick, the samurai axel has the same size i.d. on the bearing.