configuring jumbo Ethernet frames for a cluster

I know it is possible to set jumbo Ethernet frames through ifconfig [device] mtu [mtu size] and in the network configuration, but is it possible to map a particular MTU size to a specific port or stream?

We have a cluster running NFS and a MTU larger than the meager 1500 would be useful, but I don’t want to hurt our communication latencies. It would really be best to have two different backplanes; that won’t happen until our cluster is heavily used by more applications.