Okay, so I've finally found some reasonable pics and remembered another uniform book that I had in another room....
Cuirassers are fine, just swap for a pickelhaube head and extend the blanket. Paint in a white uniform and all is good.
Hussars don't work, either of them. The braiding on the Prussian jacket is much simpler, more like the WW1 style...
, also the horse blankets were entirely different. They (perhaps unsurprisingly) look an awful lot like the Austrian Hussars so I may take a look at those. Doesn't solve the weight issue but I'll just do more Cuirassers if needed.