Vincent's regiment may have numbered about 500 men at that time. Green's brigades had been sent to Texas in December 1863 for the winter so the horses could get sufficient fodder. He brought more men with him for the Red River Campaign than he had commanded in late 1863.

I've been on Henderson's Hill several times myself. If a force on top of it were properly prepared, it might put up a good defense for a time, but the position lends itself to being surrounded. That would make long-term defense of the hill problematic.