I hate to tell you this Arctic, but by using molegrips to compress the spring (as shown in your photos), you are actually increasing the torsional forces within the metal of the spring, not reducing it...
And if you look closely at each bonnet pin, you'll see a small slot in it's tip. This is so that you can insert a flat blade screwdriver to hold it steady whilst undoing the locknut, and then to turn the pin to make your height adjustment
But I'm sure you knew that really...
However, I'd be very surprised if the wing to bonnet height adjustment would ever need this sort of work, the bonnet hinge, shims and adjustable rubbers should give you all you need
