pleasuredungeon

It isn't a rotary encoder. I found your problem when testing the knob out. So I assigned it to deck seek position instead, which I find is probably a better substitute. The pitch bend buttons can act as the wind function as well.

These stick on feet may do the job? http://www.maplin.co.uk/products/module.asp?CartID=040225100446935&moduleno=1840

As Duggle said a DB9 would be a good connector to use. Rather than share switches, though these could be wired straight to a spare DIN.