Virtual netflow interface network address

I'm currently evaluating your software for my company. We're using a WRT54G Linksys router with a sveasoft firmware upgrade. This firmware is a linux os and has a module which emulates the cisco netflow functionality called rflow.

Netflow Analyzer has been working great for this setup thus far. I'm having a common difficulty in displaying OUT flows. I understand that netflow is all ingress, and that you must set the network interface address on the router and open all flows to be able to get IN and OUT working properly. Unfortunately, the module does not allow setting an interface address. Another product (NTOP) has a feature to set a 'virtual netflow interface'. This allows the application to determine which is local and which is external traffic.

I'm curious if you would consider making this feature. Or perhaps it is available to set this address in the database, or with a setting so that I can configure IN and OUT for this setup. (Without having the ability to set it in the router).

Regards