I have been here too, still messing about with the coverstitching on my vest sleeves, what a fiddly job it has turned out to be and I haven't finished them yet!!. I do have a free arm on this machine, and I have also reduced the pressure on the foot, and I am still undecided whether I like this or not - still they are only long sleeved winter vests so nobody is going to see them.
I just want to get these finished and out of the way so I can get on with something else, and this is taking far too long - perhaps what I deemed to be an easy job on these sleeves was wrong as it is quite stretchy and so difficult to keep lined up with a strip marker on the needle plate.