[TYPO3-mvc] Extendig of other model fails

[Stefan Kruse]

Hello,

im always trying to extend the In2Snippets Extension. I need to extend one
Model with a Model from me. The In2Snippets Extension is non-Namespaced but
my Extension is namespaced.
Could this be the problem that the extending not work?
I try it with:

config.tx_extbase{
    persistence{
        classes{

            \Tx_In2snippets_Domain_Model_Code {
                subclasses {
                    Tx_In2snippetsextening_Code =
SK\In2snippetsextening\Domain\Model\Code
					
          		}
            }
            SK\In2snippetsextening\Domain\Model\Code {
                mapping {
                    tableName = tx_in2snippets_domain_model_code
                    recordType = Tx_In2snippetsextening_Code
                }
            }
            
    	}
    }
}

But the new properties from me are not working. If I put my new properties,
getters and setters in the original file from the In2Snippets Extension it
works.
I think the class extending doesn't work, but why?
Thanks a lot Stefan