Yeah but what evidence do you have other than "IMO" which is possibly just repeating what is going around on the www? Don't mean to be disrespectful RGal, but someone else could say cutting a coil "IMO totally compromises the integrity and performance of the coil spring." So who is righter?
IMO's are okay, and I'm glad you said so, but theories, tests, examples, facts, comparisons, etc., are better. IMO!!
is right on the money, springs are "compromised" as seen in his pictures. To use a torch to collapse the springs can be dangerous for a few reasons. If the steel got red hot and quenched with water it might be brittle and could snap off when driving. Or, spring steel could have been annealed at the point of heat and is now soft and will fatigue and brake.
Spring steel rod rolled into a semitrical circle will push evenly onto the seat. You can see the top of his springs are now tilted creating an off-center load on the spring. I would expect to see them bowed when installed and perhaps making a grinding or squeeking noise when traveling down the road.
The real problem is they are no longer an even set of springs. Load range and installed heights will be different. The car will no longer sit level, the car will corner better in one direction than the other, the bumpsteer will be affected in one direction more than the other and can put you into head on trafic when crossing RR tracks or high crowned intersection. Also, the uneven spring rates on the front have a direct effect on the rear spring loads and tire traction in a corner.
Using a torch, cutoff wheel or bandsaw to shorten a spring is just fine, it is standarded practice for sportsman level racing. When you cut a spring shorter it WILL raise the spring rate. Racers use a spring rating tool to measure load range and installed height and can trim them to make even rated sets.
Not an engineer, but..............