Jon, do you know if the attachments that fit the Davis machines also fit any other (non-Davis) machines?
The only Davis I have in the house so far is a NVF - so that doesn't help. Though I'll be getting a bottom feeder soon. I've still got a few top clamp sets that don't fit anything. My second Davis also takes the shorter needles.
Do you know what machine takes the Boye 20 needles? It shows up as "Davis Old Style" the look to be the same length as the 10, but have full round shank instead of a flat side.