Of course, this is a religious issue so take my input however you want. I have my red cube mounted vertically on top of the engine immediately preceding the fuel distribution spider (ie after the servo). The reason this is important (and again, this has been beat to death over and over again) is that the servo determines the fuel actually provided to the engine. I have mine mounted with all steel fittings and after I calibrated it, it's been very, very accurate in predicting fuel quantity remaining. I check it at every fill up and it's always within a few tenths one way or the other of the actual amount pumped.
RV-8 #81077 Super Slow Build
Dynon Skyview HDX, Titan IOX-370, Dual P-Mags, AFP FM200A FI, Whirlwind 200RV CS Prop
First Flight 11/20/2016