The maximal size (any direction) of my player is ~90 quants.
I've created a map entity consisting of two walls (none or flat texture), some 100 quants in height and width, parallel to the x-axis (I use x/z-movement, too). The y-distance between both walls is 128 quants, so my 90 quants player can freely rotate within these limits.
When my player entity is stunned, I register it for the physics engine and vec_set(wall_map_entity.x,player.x) the position every frame. I only add torque around the y-axis and forces restricted to the x-/z-axis, so it does not look odd when (if ever) the player hits the invisible walls.