Hi. I have a Hartley Wanderer (1646). My son usually helms and I crew, and between us we are probably around total crew weight of 19/20 stone.
Ours is a sort of hybrid as we usually cruise and have done in fairly strong winds – sometimes reefed sometimes not but in the last 3 years of owning the boat we haven’t yet been swimming!. It does seem to be fairly stable at least for us.
I don’t have the rear seats but sometimes have the storage box in.
At some point we will do a test capsize at our sailing club to see what happens.