Dear Andy I’ve been adressing the same issue.I’ve modified.the hair and it’s relatively light and apparently is a new version of the Bath Chair. The buggy is a class III Shop Rider Cadiz.It is well balanced,fairly small and apart from stairs and motorways I can get just about everywhere.BUT I had to take off the ‘anti-tip wheels’ on the back,'cos they used to leave me hanging stuck on kerbs, blah blah blah.
However, by using the wheel brackets without the wheel I could create a bit of a shelf effort to put the chair on,then use small ratchet straps to hold it to the seat.I never swivel the seat and have no need for the arm rests and that would make the ‘strapping’ easier. By careful riding I reckon I’d cope.For things like train ramps I’d need to reverse on every time,which presents no problem whatsoever.
BUT,I’ve come to the conclusion that if say,I go away for a couple of days using trains I’m better off with my titchy collapsable class I Heartway Pixie which I can get anywhere on the flat that a human can walk,would be fine for use in a well sorted hotel in somewhere like Llandudno.There is the option of putting it in the glovebox of a taxi etc etc.
That’s all I’ve got to say.I hope you get somewhere with your quest and 'praps a good scooter engineer may be of help. I’ve got one ,but “Hands off”.