Loving this build..one quick question about using *external* pots that I couldn't find in the user manual / comments: 
On the board, there are 5 holes for the pots (upside down T), but pots only have 3 leads. In the assembly manual, I see that these leads are placed in the bottom row. Are these the 3 holes that should be used for all pots?  I see that there are connections between the other 2 holes (above the bottom row) to other points on the board and wondering why these connections exist if these holes aren't used. 

Thanks!