It isn't just space. The nutritional value & density of grass & browse is as important as amount of acreage. Plus Age of animals, breeders, youngsters all figure in. Rotational pastures in use, etc. Plants have different degrees of value with variety, growth, weather stresses, time of year and even the time of day! Plant a variety of forages with your grasses. Your location is also a major consideration for plants & growing season. If not all year pastures...you will need to supplement. Boer are large animals, if good genetics, and while they convert what some consider scruff to good body use, there are limits.
Sounds like no answer? Well, it is info that you need to consider as there is no magic number like "1 acre per head". Doesn't work that way. Can that size work? Yep. Depends on all those factors.