YellowFox is using Load-balancing based IP Virtual Server - a common technology in the internet. There is no need to adapt anything on the clients side.
This Load-balancing is using the the clients IP address for making routing decisions. To avoid trouble the idle time-out of your router should be set to a "smart" value of at least 20 minutes. Nowadays shorter time-outs make no sense, mostly. This is valid as well for mobile connection like 3G.
We have seen issues, if the customer is switching between providers during the same session, because of improving his internet performance. YellowFox doesn't support this type of switching. We suggest to use the same provider during an YellowFox-session all the time.