Alternative 1. Hacksaw.
Alternative 2. Torch
Alternative 3. Listen to the owner of a professionaly engineered sytem from JIC...
Sorry man, I couldn't resist.
A Subaru, Tein, Tenabe, engineer or marketing department's ass is no more caligrated that yours or mine. Since the struts are non-adjustable, you get what you get from each of the vendors, and whetehr you like it is determined only by your ass, no one elses.
My suggestion is to find a car that already has brand/model X springs and get a ride.