A friend of mine has a SBS like the one the OP is describing. I never had any trouble shooting full power loads from the hip with a two handed grip.
Now with a one handed grip the gun would twist in the shooter's hand and the lever to open the action would come back and bite the web of the shooter's hand.
"No, it's not a silencer. This little doodad is my own invention. I call it a loudener." --Sledge Hammer