Hood Springs: Heating with a torch to reduce tension (while on the car???)

Someone mentioned this in a thread recently and I can't remember where.

It was suggested that one option for reducing hood spring tension was to open the hood, open the door and point a propane torch onto the spring and get it good and hot until it starts to unwind a bit.

If this really is a reliable method, it seems like by far the easiest solution to the age old question of "where do I find low tension springs?" A question that is becoming more difficult to answer now that the vast majority of K-Car donor cars have been melted down and turned into lawn mowers, twisty ties, abstract welded sculptures at Burning Man, and Kia Forte Coupes.

Has anyone actually done this torch method? Was it done with the original hood on the hinges or off?
How do you know when you've heated them enough? Is there a worry about uneven heating (getting one spot on the spring hotter than other parts)? Is it hard to make the springs even between both sides?