Here is what a stock intermediate shaft looks like once it is shortened. This is the shortest that it can be made, by cutting out the tube and butting the 2 ujoints together.
I suppose you could shorten it up even more, by grinding the ujoints, but squaring everything up might be an issue, if you do that.
You could also just use 1 ujoint in the shaft, but unless the tranny and tcase is perfectly aligned and braced so that they never change their relationship to each other, I would be worried about driveshaft vibrations.
I would not try to run a double ended slip yoke driveshaft. For one, I see no benefit in it. For two, you aren't really going to be able to make the shaft any shorter than if you just ran a flange on the samurai tcase.