Originally Posted by
RatherBeFlying
AFMs commonly give a single arm for the crew positions, even though seats are commonly on tracks.
Parachutes (or more importantly lack of) will also affect the arm.
Many of us single seat glider owners will have the glider CG calculated after weighing with pilot wearing chute and strapped in.
I bought my first glider from a gentleman weighing some thirty pounds more than me; so I had to remove several tail weights. The fellow who bought it from me reinstalled them.
Another consideration is that North Americans, including USAF personnel, tend to weigh more and be taller; so sitting farther back.
The seats in the Slingsby are fixed position. The rudder pedals are adjustable to allow for taller or shorter pilots, so I don't think the arm of the pilots will change with weight or size. Our w&b spreadsheet gives the option of wearing a parachute. Careful fuel planning is required if you want to fly with two fat blokes and parachutes.