The only thing i would say is, that wont stop a lot of police from defecting you. When it comes to defects SAPOL are practically boundless in their power. There have been plenty of people who have shown the officer engineering papers and been told they don't mean shit, and they don't, because the defect laws are too broad. Sure regency is a different story, but by that time you've taken a day off work, paid $130, had your car gone through with a fine tooth comb, possibly re-defected for petty stuff, and gone through all the inconvenience a defect brings such as having a car you can't drive (often been given less than a day to drive, sometimes less than an hour, sometimes no time at all), all for some petty issue or something which could quite possibly be legal.
Generally speaking regency is a head screw, even if your car is safe, hell only this year my car was off the road for about 3 months because of 3 consecutive false defects for legal parts, 1 minor, 1 police major, and 1 regency major. i couldnt beleive it. the funny part is i ended up passing regency with every single "defect" i had been done for in place for the inspection.
subsequently i lost my job. which made the task of scraping together $80 for 2nd inspection + $40 for permit even harder. at least i didnt have to take a day off work haha
Sure this bs doesnt happen all the time, but tbh it happening once is more than enough. I'd be genuinely interested if there was a way you could use the engineering papers to avoid a defect, but i just dont see how it's possible, the only people that seem to really credit engineering papers are regency, and by that time you've already gone through the bs, if you're lucky you will get an officer which will be reasonable and see the papers and let you on your way, but they usually aren't the people we have difficulties with, it's the few unreasonable officers who quite simple are out to get you (recoginising how lame and immature that sounds), and they will get you for what they can, knowing the full extent of their power.