Yeah, I did it myself. You could go to the effort of talking to engineers and paying them a motza, but it looks standard if you are a good at mig welding.

Using the Zed strut inserts, (I think they were 240Z), you first need to cut enough out of the tube (below the cup). Make the first cut just below the cup, so that when you weld it back together you can merge your new weld with the existing weld. A section needs to be neatly cut (perfectly square). I used a lathe to machine the top bit (including the bottom spring cup) perfectly square, and neatly cut the remaining struts tube with a piece of tape to mark the cut line and carefully hacksawed the section out.. Now you may ask "how much needs to be cut out?", well I'd say about 50mm, but you will need to measure the difference in the insert length between the original one and the Zed one. Measure twice and cut once.

It's possible that you might run into a problem in that, depending on the strut, your spring will not be the correct length for the 240Z insert. You may need to use 240Z/260Z springs, or move the cup to suit the 1200 springs.

So these are the three things you need to think about :
1. Cutting the strut down so the 240Z insert fits in the non-Zed strut without a spacer underneath.
2. Making sure that the spring to shocker insert "travel" is matched. A spring is matched to the insert length, so using the longer 1200 springs with the shorter 240Z inserts could cause the springs to over-compress and bottom-out.
3. When shortening the struts, try and overlap your weld with the factory one, so it will pass an inspection unnoticed. Use an old insert to hold the strut together while welding. Don't overheat the insert while welding, it might explode. Make sure that the inside of the struts are clean from oil before welding.

I hope this helps
Chris