My 3320 has the 3rd function controlled by the rear remote. Those remotes are controlled by the slide lever right of the seat next to the 3 point control. That lever also controls the mid mount mower height. I have to switch the hoses form the deck to the third function. When I asked my local dealer about adding the thumb control they said not possible. I believe it is.
When I looked up the add on kit. LVB26030, it says starting with MY2011.
What changed in model year 2011?
Should I be able to “t” into the power beyond port to a 12v Electric reversing spool valve ? And add a joystick handle with a momentary toggle on off on switch ?