Invacare TDX SP Operating Manual page 114

Seat belts may not be held at a distance
from the user's body using parts of the
wheelchair such as armrests or wheels.
114
The pelvic belt should be positioned in the
area between the user's pelvis and thighs
so that it is unobstructed and not too loose.
The ideal angle of the pelvic belt to the
horizontal is between 45° and 75°. The
maximum permissible angle is between
30° and 75°. The angle should never be
less than 30°!