Never had any problems that couldn't be solved with adding/removing a bit of ballast from the counterweight or the gondola, or extending the pen out a bit further. When the cords get very long, the pen gets a bit wobbly, it pivots about it's tip too much.

I don't think the width itself makes much difference actually, I think its the angles that count, so if you scaled your machine up so it was twice as big, then it'd perform just the same, as long as you scaled up your borders too. That's certainly been my experience anyway. Of course, the cords themselves behave a bit differently when very long, there's a lot more stretch and bounce, and if you're using a fairly heavy cord (like the beaded cord) then you'll get a kind of hanging catenary situation where they end up bending under their own weight.

I made a 6m wide machine, and didn't have that problem because it was just thread and very lightweight. But it was pretty springy, so the pen itself was all over the place. That could've been reduced by more weight on the gondola, and slower acceleration, but only up to a point - the friction between pen tip and surface meant it was alway going to be a bit jerky.

sn