Somewhere I saw a strut compressor made out of two used disc brake rotors and some heavy-duty all-thread. This is not the exact post, but it will give you the idea:
Spring compressor made out of disc brake rotors.
And here is a video of it in action:
Brake rotor spring compressor in use,
I have thought about making one, but with three-- or even four-- lengths of all-thread instead of two, so the spring would be securely trapped. Of course this example is for a conventional spring and shock, so to accommodate a wider strut spring, holes for the all-thread would have to be drilled further out on the flanges of the rotors.
I'd be interested in hearing comments about this concept, and would like to see if anyone here has tried such a idea.