I talked to HandiQuilter today because we have a customer who wants to convert her Sweet Sixteen to fit a Little Foot Frame. The Simply Sixteen is made specifically for the Little Foot frame. It doesn't have any back handle bars, and the screen and carriage are different. However, you can find lots of used HQ16 that can go on about any frame. It's kinda confusing because there are 3 different HandiQuilter "16" machines.
#1 is the original HQ16 (you can find lots of used ones, but I don't think they make them new any more).
#2 is the Sweet 16, which is a sit down machine -- no carriage or handle bars.
#3 is the Simply 16, which is specifically made for the Little Foot frame. It would take some adapting to make it fit on the other HQ frames, and I don't think they have kits to do that.