I've had 5-6 MSFF2 sticks, stripped, repaired and modded. Both Red trigger and grey trigger.
Here are a couple
As far as I can see there is no significant difference between red and grey - it is cosmetic, they seem to work the same and the internal parts are interchangable. I think the Red trigger were later and therefore newer. But now newness is less important than how much the stick has been used.
When you buy on E-Bay they often arrive without the power cable. People sell them because they haven't used them in ages and don't remember where that cable went. However it is just a simple cable identical to dozens of other houshold items. The different voltages and cycles of USA/European power supply are dealt with by the transformer circuit board within the stick.
It is also common to find that the trigger and other switches on the stick are U/S after having been brutalised by brats playing shootemup games.
There is one pot in the stick, it's in the handle giving the rudder axis. This is a nasty small plastic cased item which is often spikey or not working at all. The seller probably never needed that axis so won't have noticed it doesn't work.
If you are paying a good price, ask if the power cable is included, ask if every button works, ask if the rudder axis tests clean in control panel calibration. A perfect stick may go for 100+ Dollars/Euros. Personaly I have bought them from 1 Euro up to 50 Euros and expect that it won't be perfect (strangely enough the 1 Euro stick was perfect and several who's sellers claimed they were in fully good working order weren't). These are heavy items and postage costs often make it too expensive to send it back for refund.
The X and Y axes do not use pots, they use sensors, I think they are Hall sensors, but I have never had to touch them. They are incredibly reliable very precise, do not break, do not need recalibrating.
The light sensors are in the handle to see if you are holding the stick. When changing the handle I tape these blind and put a table light switch on the power cable so that I can switch it off when I'm not flying.
Now why would you go through all this trouble when you can go down the local shop and buy a $25 stick with guarantee?
Well on the 777 IL2 Battle of Stalingrad forum they had some pictures of the BOS/ROF development team. Here is one :
Now what is that on the desk and on the shelf behind.
I wonder why the FF2 works well in ROF?