Contact open books with flexible pages

We give an elementary topological obstruction for a manifold M$M$ of dimension 2q+1 > 7$2q+1\geqslant 7$ to admit a contact open book with flexible Weinstein pages and c1(pi 2(M))=0$c_1(\pi_2(M)) = 0$: if the torsion subgroup of the q$q$-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 integral cohomology. We also produce examples of non-trivial loops of flexible contact structures using related ideas.