Yes another SYE ? Confused

I have read pretty much all the SYE threads and am Confused.
I have an NP242 and will be using 3103-27CV Yoke
My question:
What is the proper lenght to cut the tail shaft ?
I have read and come up with 3 different answers.
This thread says 1.65" of spline
http://www.naxja.org/forum/showthread.php?t=1015603&highlight=slip

This one says 1.25" of spline
http://go.jeep-xj.info/HowtoSYEconversion.htm

And I think it is IRO says 1" of spline

Using the 3103 Yoke, cutting the splines anything less than 1.65" is going to be less than 1" of spline engagment

Which is correct ?

Also what is the proper size to D&T the Shaft ?
One says 3/8" Tap using 21/64 drill
Another says 3/8" Tap using 5/16 drill

Again which is correct ?

Personally I would cut such that at full compression (including compressing the bumpstops fully), you will have about a quarter to a half an inch of travel left in the driveshaft slip joint. That will maximize both spline engagement on the yoke and droop/compression capability, though it's harder to determine the right number than just following a guide.

As for the drill - a 5/16 drill is 20/64, it will be harder to tap but will result in greater thread engagement. I'd go with whatever drill the tap you buy suggests, some taps will even come with a properly sized drill (mine came with an O-size drill.) Also, drill FIRST with the next diameter down, then redrill with the recommended size, this will produce a smoother more even bore as it won't be overloading and overheating the drill. If you are paranoid you may want to center drill about 1/8" deep first using a small (1/16 or 1/8) drill to make sure the main drill centers easily.