We present the results of the first complete calculation of the tree-level
2→2 high-energy scattering amplitudes of the longitudinal modes of massive
spin-2 Kaluza-Klein states, both in the case where the internal space is a
torus and in the Randall-Sundrum model where the internal space has constant
negative curvature. While individual contributions to this amplitude grow as
O(s5), we demonstrate explicitly that intricate cancellations occur
between different contributions, reducing the growth to O(s), a slower
rate of growth than previously argued in the literature. These cancellations
require subtle relationships between the masses of the Kaluza-Klein states and
their interactions, and reflect the underlying higher-dimensional
diffeomorphism invariance. Our results provide fresh perspective on the range
of validity of (effective) field theories involving massive spin-2 KK
particles, with significant implications for the theory and phenomenology of
these states