Try keeping the male in A/C around 78-82F (during the day) after brumation without any supplemental heat WHATSOEVER. No heat pads or tape...nothin'.
In the wild, subocs hardly ever are in really hot conditions. They shun the sun, will only come out at night (or rarely at dusk). The Chihuahuan desert is cooler and more humid at night than it is during the day.
And during the day, subocs sleep underground in the rock labyrinths and bat caves beneath the desert floor, where it is cooler and more humid than above ground.
If you've ever been in a cavern in the desert, then you'll understand what I am talking about.
So it is quite understandable that this species might be more succeptible to sperm being killed by heat than many other species.
Keep the ambient air dry (A/C does this well) and the cage well-ventilated and you won't have many problems.
It also doesn't hurt to keep a cool and slightly damp retreat with this species (I think it actually helps for several reasons).
Try that and let us know if your breeding efforts succeed next year.
Dusty
Suboc.com