Gland Depth x Groove Width (area of the gland) must be larger than the cross section area of the o-ring (Pi x R^2). Otherwise many bad things will happen to your design.
Make sure the squeeze % is sufficiently high enough to seal, but low enough to allow dynamic movements.
Squeeze inches = O-Ring cross section diameter in inches - Gland Depth in inches
Squeeze % = Squeeze inches / Gland Depth in inches