You hang it from a nail in the rafter , and pull down.
If your lucky the wingtip lands on your bare toe , when the nail pulls out .
A piece of paper or cardboard , cut , and taped ( drag a finger across to de stickyfy mega sticky tape - so it dosnt ruin the paint )
thrown thru the end , maybe with a notch for the wire & neutral line pre drawn , pencil full deflection marks on it ,
the get a protractor , pull out the stencil & measure on the bench .AND youve got a record .
Just folding a corner ( 90 deg. 0 of paper gets you 45 deg , for a rough ' exact ' check .
Depends if the last bit ( off travel ) is gooey . As in , if youhang it on one leadout - is it ' at the stop ' or does the pulling on it ( Ahem ! )
get more ' shift ' off the flaps , etc .
CAREFULL .
Er .
Theres anther thought , having overmuch movement - free - and setting handle radtio for useable movement , if you loose it & gotta run ,
whacking the handle flat , can get a ' stall turn ' ' avoidance ' out off it . Whaking back the handle hard, when its freeflighting downhill at
four foot , can pull a lot off the inertia / speed out of it . Extreme measures for extreme conditions , or loose units .