Gentlemen,
Just my experience :
This "tweak" just destroy fps performance on my machine.
For instance my home airport LSGG (Geneva Switzerland) with Orbx sceneries (Global, Vector, Europe) + Pilot FSG2010 FTX - Ultimate traffic set to 80 % - GEX clouds, etc...
Intel Core I7 3770S CPU @3.10 Ghz - 3101 Mhz. Somewhat low range NVIDIA Geforce 735M GPU
Result :
OPTIMIZE_PARTS=0 (original) setting unlimited / average 30 fps, peak up to 40+
OPTIMIZE_PARTS=1 (tweaked !) setting unlimited average / 18-19 fps, down to 14-15
I can understand that maybe with a much higher range graphic card this tweak can be somewhat useful, but for me all I can say is : just forget it!