I have tried all kinds of supports. The Sagework is simply the best and easiest to use. I have 3 of them - one for each guitar case. I also recommend the shorter version which works perfectly when you kick back on lower chairs.
I exchanged the regular size support arm for the short version and for me it is so much more comfortable..
It is great that the Sagework support allows for this kind of adjustment as it is hard to know which size is best for you without trying it out for size.