Next we've got the seat strengthening piece that sits under the outer runner and attaches to the floor
This with what it looks like when Barry makes one - fantastic work!
The top half of mine was in good nick, so I decided to just fabricate the bottom half. It wouldn't be as pretty but will be plenty strong enough. As you'll see from Barry's piece the flange along the bottom has a step halfway down. After thinking this through I decided to make it in two pieces

(The bent bit in the flange is to fit around a bump in the floor)
I went to fit it and found a bit of corrosion I'd forgotten about - and realised I'd need to sort that before I could weld on the seat strengthener.
Piece made and welded in
Then welded the two seat strengthener pieces in
Then we went to a friends house for tea and cake. Hurrah!