Hello mjb34500,
I have got a Massey Fergusson 35 and I converted a Backhoe used on a skid steer to 3 pt mounting. After lifting it with the 3 pt it is secured by adjustable rigid beams to the tractor at the fixing points just below the top link attachment. The first picture shows the backhoe with my simple thumb. The second is a close-up on the mounting. You can see the yellow beams going to the same pins as the 3 pt and also the yellow top link, which is forked at the tractor end going to the same fixing points as the beams. Unfortunately I have no picture available showing the tractor ends and as I am not getting back to Sweden for another month so I cannot get a better picture now.
This arrangement has worked for me without problems although the output from the hydraulic pump in the tractor does not allow speed digging. It is working fast enough for my needs.