I'm not trying to be a "range lawyer" here, but your situation will depend on the specific stage description.
On a stage that ends with a string or target array that must be shot weak handed I wouldn't think there would be any problem with shooting the entire stage weak handed.
If the stage includes both strong and weak hand strings, I don't think you have any choice but to shoot with both hands or take a penalty.
You might check it out with the match director before the match. It never hurts to ask and most officials are willing to accommodate any situation as long as it's fair to all.
Good luck and good shooting.