Maniac ... you are correct. I find it easier to do ruler work on an LAQ than a domestic (even a large sit-down domestic). But I'm not giving up on either (I'm still in the practice stages of both!).
You first need to make sure that you have a presser foot that is suitable to ruler work. Ruler feet have a much deeper foot so that when the foot is on "down" bounce it doesn't slide under the ruler. Most of the regular FMQ feet are as flat and small as possible and they can very easily slide under the ruler as you are moving the fabric. The ruler foot has a deeper "well" that the needle sits in. It's almost impossible to see where the needle is actually hitting as you sew, but if you are using a ruler, it shouldn't be an issue because the ruler is your guide.
Make sure you have a flat surface long and wide enough to hold the entire ruler, don't let even an edge hang off, or rest on a hump. The entire ruler needs to be as flat and stable as possible.
Sticky tabs for the under side of the ruler, and upper if your fingers need them.
After that ... practice. That's where I am at. I have a quilt I want to use ruler work on, but until I'm really comfortable it will remain a UFO!!