hello from Russia!
Need help with this task.
It's about 50 members on standart proxy server KerioWF. I want to create proxy on RouterBoard like RB/800PI.
But it's problem with autenification by login and password, cash and biling.
For all this tasks its need to use HOTSPOT, web proxy on port 3128, CompactFlash card for cash and billing program.
Do someone use this schema or its wrong?

yes, for authorization you should use Hotspot.

for billing you may use User Manager, installed on the same machine, or use another machine with any other RADIUS server

there should be no problem which ever proxy you use. Just look at you hotspot configs