Please change your write-up to instruct people to use spring compressors to remove the stock springs.
I'm sure the BRZ/FRS stock springs are not compressed very heavily, and your DIY method works just fine.
But we, as a forum, need to be over-cautious when instructing members on car repair methods. The last thing we need is some kid thinking it's easy to remove springs without proper tools. They might be successful on the BRZ, but what happens when they try it on another car.. something big an heavy and much more highly compressed.. they could get hurt really badly.
Please err on the side of caution when doing DIY guides. Homebrew methods are great.. but only when there are zero safety implications.
Other than that.. excellent writeup! Thank you for taking the and energy to document all the steps with pictures and graphics. Nice work!!!