Great tip. A point about torque on a fastener that most people ignore is that the fastener has to be moving when the torque is reached, or it isn't accurate. What this also means, when using a torque wrench that clicks when the number is reached, is that multiple clicks (or multiple pulls if using a luggage scale) doesn't 'improve' or 'verify' the torque.
I happen to be working on the water pump and thermostat in my 987.2 Boxster. All those bolts are super tough to reach and like you, I don’t have the Porsche tool (though theirs is pretty cool, not insanely expensive and I might buy one if I could. But I’m not a dealer). That nut on the belt tensioner loosened and I was dreading trying to fix it. An experienced hand, I think I could use my torque wrench on the fasteners I can reach and use muscle memory to duplicate. Now I won’t have to try that either. Thanks mate!! Now to find a luggage scale….