Very dangersous. Waivers do not provide absolute protection; at best, they provide protection from the normal risks of a sport, *provided* that you provide the normal, expected level of safety. That is, if a fighter is injured because the surface of your ring is is not good or appropriate; or because you (or whomever is officiating) did not step in promptly to stop the fight if one fighter is getting hurt; or because you allowed too much of a mismatch in weight classes or didnt't inspect gloves properly; or if you didnt' have medical care on stand-by; etc.--if anything like that happens, which would not happen at an "official," regulated match, you could be liable despite the waivers. And if you were liable, it's almost a given that your homeowner's insurance would not cover the loss/costs, since regular homeowners does not cover sporting events on the property.