Thanks everyone for the responses. I failed to mention that the building is nearly complete. With some trial and error, I think we have a solution. There were some fairly painless upgrades to some "non-gym" areas that have reduced what is needed in the gym. At this point, com-check will work if we have a R8 continuous on the CMU and only above 10' AFF (to minimize impact damage).
The plan now is to find a product/panel that can be applied to the inside surface of the CMU that will also give us some acoustic benifit. Web surfing tells me there are several choices but the suppliers are still sleeping!