Setting up overapplication in 11.5.8 to specific customer profile classes

I am trying to change the automatic application of receipts in Receivables to allow overapplication but for specific customer profiles only. The following settings have been changed:- Lockbox - Allow Overapplication - Yes, Receipt matching by Transaction number; Autocash Rules - custom set up (1 - Match payment to invoice, 2 - Apply to oldest invoice first, automatch rule - On Acc)removed from our customer profiles of Trader, Public Bodies and School, and kept in place for customer profile Ordinary. Selected transaction types - set to Allow Application.
When I have imported a receipt batch through the lockbox and then run quickcash the vast majority of receipts are unapplied, even those from customers with the Ordinary customer profile which have all auto cash rules still in place. Overapplication has occurred on only two receipts and these are for customer accounts with Trader customer profile the remainder of the amended profile receipts are unapplied. Have I missed a vital part part of the set up?