The reality is that anything about HST except for the principles is optional. You like others will likely find that you get the most out of HST by tailoring it to your specific needs. Based on what you’ve described (your already trained, do active work and have no connective tissue issues) then you are likely not going to get that much from the 15s and would be a good candidate to skip them from the start.
Male: 51 years old
Bench Press 240 lbs. @ 178 lbs. (12 July 2012)
Power Squat 390 lbs. @ 180 lbs. (10 November 2012)
Deadlift 390 lbs. @ 180 lbs. (27 November 2012)
Total 1020 lbs. (finally made it 16 July 2012)