A multiple-mirror DT reactor with injected power supplied by a fast neutral D beam is considered, and the power-balance equations for the hot and warm components are solved. For a fixed mirror ratio M1 and fixed Q = fusion power/injected power, the warm- and hot-deuterium fractions, the warm temperature, and the injection energy are determined so as to minimize the plasma pressure-reactor length product p1L. The equilibrium hot-ion distribution and the energy transfer factors are found analytically from the Fokker-Planck equation. For Q = 2.8 and M1 = 3.3, it is found that the additional hot-component fusion reactions produce a 26% reduction in p1L, to 4 × 105 bar·m. The seeding of the plasma with low-Z impurities so as to reduce the axial power loss has also been considered. Using a corona equilibrium model and optimizing the impurity fraction, an additional 10% reduction in p1L is obtained.