Regarding FM changes, you can do a lot to the FMs and the AI will still fly fine. The warnings against doing this seem like a bit of a red herring.
Now, for horse power, changing it does nothing (same is true of RPM). Aircraft performance in WOFF seems to be a function of the max sea level airspeed, the weight, and the LDmax (lift/drag). "170hp" is just a generic designation for the Mercedes D.III power output in the Albatros D.III or D.V. Primary sources indicate 175 PS @1450 rpm, with the max rpm in level flight at around 1500 rpm.
Now, regarding weight, there is a Windsock document that has the OAW Albatros D.Va coming in at over 950kg. We also have a primary source that says 914.5kg. So, I went with the primary source for my WOFF FM. That same Windsock document doesn't convert correctly between metric and imperial units, fwiw. They say 5km = 15250ft.
The other big difference you can feel in the FM I made is the rudder response. No more hockey skids to the point of flying sideways through the air. I also reduced the roll rate slightly to feel more like the Rise of Flight Albatros D.III. Every account I have read of the Albatros describes mediocre roll performance, and with all the subjectivity that comes along with it, it seemed appropriate to make that change.
Incidentally, the WOFF FM leaves out the 2 degrees of lower wing dihedral in the Albatros V strutters. I was very surprised that they missed this.
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Now, having argued myself silly at the Rise of Flight forums over the Albatros airspeed, it is great that I can finally tinker with the FM in a WW1 flight sim. However, WOFF is not free of the same problems. Just like Rise of Flight, the Entente rotary scouts are pretty fast. 118.5mph for the Camel, 110mph for the Nieuport 17, 116mph for the Nieuport 24, etc. As Pat Wilson says, FMs will never be perfect, but they shouldn't be obviously wrong. The idea is to make the relative performance of the aircraft credible. So, one of the first things I did was to slow down the rotary scouts (including the Dr1, ahem). For example, all of the more detailed sources have a max airspeed of about 107mph for the Nieuport 24, but there is one figure out there that says 116mph and WOFF went with that one. That ends of skewing the whole balance in 1917 when your Albatros is slower than 116mph.