PASS: elliptic torsion orders, labels and all Kummer triples.
PASS: explicit HLP model, discriminant and nonconstant elliptic j.
PASS: conic parametrization, matching and the constant nonsquare obstructions.
PASS: subgroup presentation has invariant factors [4,16].
Fixed elliptic factor: #F(F_11)=16.
Fixed elliptic factor: #F(F_13)=16.
PASS: fixed elliptic factor has exact torsion [2,8].
PASS: t=-1 seed is Q-isomorphic to census 4.16.a, exact torsion [4,16].
PASS: s=2, t=-19/49 has exact [4,16] and is not Q-isomorphic to the seed.
ALL ASSERTIONS PASSED.
CERTIFIED: split [4,16] family identities and exact torsion calculations.