  We review the experimental constraints on the parameter $\alpha$ associated
with the Generalized Uncertainty Principle (GUP) and the parameter $\beta$
associated with the Generalized Event Horizon (GEH). The Compton-Schwarzschild
correspondence implies a relationship between $\alpha$ and $\beta$, with both
parameters being of order 1. This presents a problem for our previous `$M+1/M$'
model since the extra gravitational force at sub-Planckian masses contravenes
observations. Various resolutions of this problem are discussed.
