I am 95% sure I will buy a 115mm (Teleskop Service) triplet in the upcoming weeks, it will ride on a manual equatorial or a manual altaz mount and it weighs 7 kilos with rings and Vixen rail. A 2" diagonal (450grams) plus a 30mm or 50mm finder (at least 300grams) will complete it, and my heaviest eyepiece weighs 850 grams. That's 8.6 kilos total but probaly a half-kilo more because my smaller apos need a sliding counterweight along the tube and this bigger one can't be an exception. We're talking 9 kilos in all likelihood.
So, how much counterweight will the mount need?