  We show how to fix the renormalization scale for hard-scattering exclusive
processes such as deeply virtual meson electroproduction by applying the BLM
prescription to the imaginary part of the scattering amplitude and employing a
fixed-t dispersion relation to obtain the scale-fixed real part. In this way we
resolve the ambiguity in BLM renormalization scale-setting for complex
scattering amplitudes. We illustrate this by computing the H generalized parton
distribution at leading twist in an analytic quark-diquark model for the
parton-proton scattering amplitude which can incorporate Regge exchange
contributions characteristic of the deep inelastic structure functions.
