I found this project ->
https://github.com/ryomuk/XYamp which is a deflection amp design for use in conversion of B/W Watchman pix tubes to vector (XY) mode.
It allows deflection coil compensation - meaning that yokes wound for raster scan can be driven as vector without problems. So, yoke rewinding is unnecessary.
My question is, can this amp drive deflection on regular 5" tubes, as used in many portable B/W sets? It only appears to have been tested with the special flattened Watchman tubes which have weird deflection. Due to my limited understanding of electronics I don't know everything that the amp is doing in the schematic though. But, if it's on a breadboard (which it is) then I can probably build it.