Thank you guys fo all your answers. You raised some very good points here. My question has been provoked by an invitation that I have received recently. It came by regional (East Europe) federation for free fights. There are fighters from any style, age and size. Most of them are practicing Karate (any type), Kickbox, Judo, Box, Taekwondo, Sambo etc. Unlike most of the Karate tournaments there are no categories. The competitors are paid and do this for living so it is a serious decision to be made. I think that I will try and if not will continue training for health and spirit. P.S. Most of the guys I met in the dojo (more like training hall) are around 6`3/ 100-120 kg