I just do a 15 minute warmup up to SST then the test. I get the same results as I do using the coggan method but not as decimated/painful.

Honestly I believe good testing is all about good pacing or knowing what you can or can not push for 20 minutes. I have seen way too many people either hold back too much or go out too hard. I believe Coggan's method is designed to address those that tend to go out too hard.