I’ve decided that these struts are actually far too strong and I’ve taken them off because of this. I needed to help the left hand one to begin to move when closing the bonnet. The weaker right hand one looking into the bonnet could hold it up on its own, and measured at 14kg when I tested it. The left hand one needs a load of 29kg to overcome the sticktion before it begins to move and is then a steady 20kg. I’ve ordered some 100N struts (10kg) from SGS which are direct replacements and can use the IL-M brackets and ball mounts.
I chose black painted replacements instead of stainless because those in the boot are black with body-colour brackets, I painted the IL-M brackets to match the rest of the car. Now the lifters at each end look in harmony with each other and with the car, and the brackets look like they have always been there.