I resolved my feed dog issue and spent some time this evening making spirals of varying sizes on my double slice quilt. Fun!
Boring antique sewing machine babble: from what I've heard a Singer 66 is not considered an ideal quilting machine. That's because it has a drop-in bobbin, which means the bobbin thread has to come out of the bobbin and take a turn to go up into the machine. This puts stress on the thread. A great quilting machine is the Singer model 15...I have an electric one from the 1930s, but it needs to be rewired and I haven't used it yet. I don't know how the thread path of a 66 compares to a vibrating shuttle machine, and which machine puts more stress on its thread. Maybe if my 27 works, then my 66 would work too. I suppose it wouldn't hurt to try, though it would be a pain to wrestle the 27 out of its cabinet and install the 66. I suppose it'll just depend on how much I hate changing the bobbins out.