Turning on selfdamage obviously helps but you've already done that in the replay you posted.
Try using a smaller/lighter body part to slam into the torso instead of everything under the abs. for example the knee.
If you want to make a huge boom using lots of joints (like chezda's hit in prolulzstuff default folder) you must have a good setup and put some speed into your hit. Flying away from Uke in a upside down position cant get you that.
Keep your balance and control Uke