(Bob)
If the procedure for removing dual controls is in the flight manual
(which it isn't) then it's in the maintenance manual which is intended
for the authorized maintenance "entity" be that a repair station or a
mechanic with at least an airframe rating. This goes for aircraft
registered in the "normal" category.

Bob
Has been a few years but I believe if you check the flight
manuals Weight & Balance sheets, section C or ( form C ), you will see a
check off box that requires a check if the duals are installed or
removed. Should also have the date, initials of the person who performed
the task and a correction of the weight & balance.
Weight & Balance sheets, isn`t that one of the things inspectors like
to look at on ramp cks. :-)