The old Shopper Group & Payment Module question... again

[radianation]

I've seen a lot of questions and I haven't seen any solid answers. First off, I can't easily upgrade to the latest version due to some customizations in place and lack of client budget to compensate us for those improvements at this time. With that being said, I would like to understand how I can assign payment modules correctly to shopper groups.

Currently, we have many shopper groups that are set up in such a way that they restrict users from seeing products outside of their shopper group. There are two groups, however, that we want to give the option to use COD as a payment method simply because they don't have to pay for the virtual downloads and can access the files directly for free.

For some odd reason, other shopper groups are also able to see the COD option as well and some have started to take advantage of it.

How can I assign the Paypal Pro payment option to all groups and the COD option to only 1 or 2 groups as necessary?