Today I finally got round to changing the height of the rear suspension again. I needed to drop it down 25mm that meant changing the 75mm extension to 50mm. The process was quite straightforward once I had the strut removed and the 3 extenders off, then each one had to be drilled a further 25mm using a 9mm drill for an M10x1.25 thread. I drilled down through the existing thread and when I hit the bottom, zeroed my height on the pillar drill, then drilled down another 25mm. The drill started squealing on the first bolt, so I needed some lubrication to help it along. All I could find was some 2 stroke oil, but it did the job. I had to drill about 2 - 3mm at-a-time then bring the drill out to clear the swarf, also my drill was jamming when I tried to go too deep without clearing it. I clamped each bolt in the vice and ran a cutting tap down, followed by a plug tap to get to the bottom. I also used the 2 stroke oil to lube the tap. I then set the bolt in my vice so that 25mm was protruding from the vice jaws and then carefully cut through with an angle grinder. I used a thin 1mm disc that is normally used for stainless steel. I find these cut better and neater too. A quick touch up with a hand file then ran the tap back down the start of the thread. Then fitted back onto the strut. I put the struts back on, wheels on and dropped it back down on the deck.
----I am happy with the height now. Just dropping 1 inch has changed the look of the car and now the relationship between the wheel and the wheel arch looks good and regular. It also by coincidence looks about the same as the front, just luck.