On Sunday, September 29, 2019 at 10:45:20 AM UTC-7, wrote:
Does anyone know if it is safe, assuming you are properly trained in aerobatics,
to perform loops, rolls and inverted flying in a 1-26E?
Glider is rated at +5.3 -3.3 Gs

As already mentioned the 1-26 was rated aerobatics and later that was probably removed for liability reasons. I could be wrong, but I have never heard of a catastrophic failure in flight. Some severely damage but it still flew. Many years back in the SSA archive is a picture of a 1-26A with fabric top section on the main wing was gone after some high G loops were preformed. Front section of the wing has a aluminum skin and that was all that was need for the plane to still fly. Pilot landed OK. There was a severely buckled spare near the root of a 1-36 after some one did the high speed barograph notch off tow. Plane remained flyable.

There might be better planes for aerobatics, but none as fun as a 1-26 with a sport canopy to get your blood flowing. There use to be one at Dillingham in Hawaii.

Soaring_June_1983.pdf page 22 1-36 spar bent

George Powell's "Wild Ride in a 1-26" page 8 Soaring_July_1991.pdf 1-26 lost fabric

BG