With the middle sill welded into place this again was coated in a couple of coats of weld through primer to hopefully help to stop the rust coming back. The outer sill is another god replacement panel but it is quite long and tricky to handle, it is important to have plenty of different types and sizes of clamps as you need to have it under control so you can put some self tapping screws in before welding. One happy with the fit (it will take a lot of trial and error and a bit of work to get it to fit correctly) check with the door to make sure it lines up with the swage line down the door and that the gaps at the bottom are equal. Run a 8mm drill round the bottom of the door and make sure it does not catch or rattle too much on the way round.
The outer sill was then tacked in place before being fully welded in when totally happy with the result. The front of the sill has a closing panel that has to be slotted into the hole on its side and then pulled forward to get it to fit on the front flanges. The best way is to weld a handle onto this panel, it allows you to pull the panel back so you can get a quick tack weld onto the panel and sill front. Once I had done this I painted as much as I could on the inside of the sill and A post lower with Hamerite to hopefully keep the tin worm away.
The A post also has a filler panel which has to be welded in to complete the sill. The rear of the sill connects to the rear wing so will be left for now and will be welded up when the rear wings are replaced. This was repeated on the other side of the car so up to now I have replaced 2 floor pans, 2 inner sills, 2 middle sills, 2 outer sills, 2 A post lower repair panels and 2 A post filler panels.