3) As can be seen in Tony's photos, you need to mirror the fish plate along the rivet line. It should tie in at
12,1 cm and
25,7 cm from the last cross member.
The late chassis with pintle spring in between chassis rails has two fish plates on top and bottom. My 1943 chassis is the earlier one with pintle spring below the chassis rails, these only have a fish plate on the bottom.
Hope this helps, let me know if you need more measurements. Maurice lives near you, you might be able to do some detailed measurements yourself.
Hanno