I think the older vertical bobbin machines might have been more forgiving. I used to use Elna shank and feet on a Pfaff 1471. Bought a Viking 1+ and that used the same feet. Some also fit a Brother PC 6500, and an Ellure. I've used other low shank feet with ankle attached on all machines. It could have been stitch width. Earlier machines were all 6mm. Pfaff came out with the 1473 and changed to 9mm. I have some 6mm feet, but use the twin needle button for safety.
Just make sure the needle and the hole line up.