The Twin-2 Acro is built stronger than the straight Twin -2 with an extra layer of uni-directional cloth over the spar, steel push-rods, rudder pedal loops, etc. Buyers of the Acro would most likely anticipate more than an occasional loop or spin. The G-103 Twin-2 Flight Manual authorized "loops", to show the ship is built strong enough to take the forces generated by a properly executed loop, but does not have the extra strength of the Acro. Most G-103's are over gross weight with 2 average sized pilots wearing parachutes and this has a direct effect on how many G's you can safely pull.
Hope this answers your question,
JJ