i have made plenty of drive shafts in the backyard. i have never made my own CV joint or double carden though. if you look at, it has a middle "balljoint" along with the 2 ujoints. really not possible to make that with just 2 ordinary yokes.
cutting the yokes off so you can reuse them is the most important. i usually cut right on the weld so that there is enough meat for shaft tubing to get a good seat and for adjustment purposes.
if i need to make a driveshaft with a CV joint at one end and a slip yoke at the other. i just find 2 driveshafts with what i need and try to get them with similar diameter tubing or just go the custom driveshaft place, buy new tubing and cut it length, then weld on the ends.
to make them as straight as possible, take 4 small castor wheels and screw them to your bench, 2 at each end of the shaft so that the driveshaft can rotate and use a dial caliper to test the heights and make it within .005 and you should be good.
i have made plenty like this and have never had an issue of them blowing up or anything. just make sure you use a decent welder.
if you ever need some help just pm and i can help my best.