  We use partial wave unitarity to constrain various bespoke four-point
amplitudes. We start by constructing bespoke generalizations of the type I
superstring amplitude, which we show satisfy dual resonance and have suitable
high-energy limits. By analyzing the behavior of partial wave coefficients for
highly massive states, we strictly rule out all bespoke amplitudes with
asymptotically non-linear Regge trajectories and place constraints on the first
few non-trivial parameters in asymptotically linear cases. Finally, we argue
that while a large class of unitary bespoke amplitudes fails to satisfy Regge
Sum Rules, there exists a smaller sub-class with a vanishing mass gap that is
superpolynomially bounded.
