One of these has been on my tuit list for at least two decades so I reckoned it was about time I made one This design, in my very 'umble opinion, is the best one out there by several light years but it's not mine: it's based on one I pinched from Mitch Peacock's UToobing channel; see here
It's fully adjustable in both planes, firstly by slackening off and pivoting the frame about one of the coach bolts and secondly by a cunning system of adjustment on the top track using a couple of packers to set the exact angle.
...and just to and a little extra poshness, I lubricated the tracks with a smear of...
...Alfie Shine. Much to my surprise 'cos it doesn't happen often it was spot on first time! - Rob