I never have seen anyone complain about not being able to swing an Excel or Edge all day, which were the latest Fisher designs. Swinging a CZ-20(6 lbs.)shaft mounted all day is a different matter.
The under the arm cup weight distribution for the M6/T2 presents environmental problems. I know everyone is involved in different aspects of the hobby but the idea that you have a portion of the detector prone to moisture damage close to the ground is not particularly appealing. Wading on lake sides, river banks, and saltwater beaches makes this style of design a questionable choice. Detector stands are available, but when they reach the size to assure sufficient ground clearance they add weight and can become an impediment to swinging the coil. Trying to work the walls of a cellar hole and having a detector stand jab you in the leg gets old real fast, been there, done that.
Also, maybe I'm in a minority, but I do hunt in rain, sleet, snow and flying ocean mist, otherwise half the year is lost afield. Trying to waterproof those two designs looks iffy at best, whereas the single enclosure designs have very simple and easy solutions. I did give some consideration to the M6 when it was released as there were some indications it might be able to hunt saltwater beaches, but the under arm pod has given me pause.
Now if the under arm pod was for batteries only with a gasketed watertight cover and no headphone jack, then the F75 would be an improvement over the T2 design, but I don't see that happening realistically.
HH
(High Moisture Content)
BarnacleBill