  We give an elementary topological obstruction for a manifold $M$ of dimension
$2q{+}1 \geq 7$ to admit a contact open book with flexible Weinstein pages and
$c_1(\pi_2(M)) = 0$: if the torsion subgroup of the $q$-th integral homology
group is non-zero, then no such contact open book exists. We achieve this by
proving that a symplectomorphism of a flexible Weinstein manifold acts
trivially on cohomology. We also produce examples of non-trivial loops of
flexible contact structures using related ideas.
