Some random notes about the stick mechanism from my experience building
and installing a retrofit cockpit control stich mechanism:

* The way the two aileron bellcranks are located below the axis of the
stick's pitch pivot, there will be rather a lot of unintended mixing of
pitch input into the ailerons. The usual way of avoiding that is to
place one or both ends of each transverse aileron PP tube near the
pitch pivot axis. They don't have to be right on the axis, just close.

* That other poster is right, the blue reversal bellcrank behind the
seat is probably something you can do without. Parts you leave on the
ground can't break in the air.

* If you want to see some really elegant ways of implementing control
sticks where you can't fit anything under the seat pan, have a look at
a European sailplane.

Bob K.
http://www.hpaircraft.com