The fuselage covering is very significant to both longitudinal and directional stability of any aeroplane. If you remove that, from an aeroplane designed to have it, there is a very high risk of creating serious handling problems. The largest and biggest problem might well be the aeroplane trying to fly sideways.
Generally fabric covering does add to strength, but usually aeroplanes are not designed to make use of that strength - aeroplanes are stressed and tested structurally assuming that the fabric isn't there. (Not true of metal skinned aeroplanes of-course).
So if you strip the covering off, the aeroplane may not be safely flyable, but shouldn't actually break until you hit the ground out of control.
G