The BGA data sheet does indeed give a maximum seat loading of 110kg front and rear. However the total loading of the empty airframe and cockpit load must not exceed the BGA max AUW
Many BGA 2 sweaters have hugely reduced rear cockpit loading limitations if the front seat is fully loaded. I flew in one with a 70kg max rear seat load when front occupant was 100kg
Hence read the placard before launching. Our 2-seaters have a little chart that gives details for normal & aerobatic flight, however there are few people too heavy to fly (and they will take 110kg in both seats), just a few how need to put a weight in.