Thanks for the idea... I found two photos of the back side of the Power Dome cassette. One version had a solid disk but there were some lines on it that make it look like it's a cover. These are the ones that you can see the company logo on the back of the cassette. Can't quite tell what's going on there, structurally. The other version had a spider cut into the lowest cog and it looks like there's not enough material there to enlarge the hole for the freewheel body, but that opens the possibility of an adapter. I think the dome probably needs the high-gear spline too, how would you deal with that end?