[TYPO3-mvc] access Attributes of IRRE relation

[Thomas Mammitzsch]

hi list,

i want to store an attribute in a IRRE relation. I have the following:

Customer n:n Insurance

The relation should have the calculated Rate for the selected Insurance. 
I made the $TCA part, but have no idea how to access it with extbase. I 
tried to make a Model for the relation and added it as a property to 
Insurance, but the property doesn't get set.
Is it maybe a naming thing?

The TCA array is $TCA["tx_myext_customer_insurance_rel"], the domain 
model is called Tx_Myext_Domain_Model_CustomerInsuranceRel.

What am i doing wrong?

regards, Thomas