Any tuning of this parameter needs to take into account the characteristics of the network, in general increasing the size of this parameter to 4096 will reduce the number of network requests and therefore reduce the latency inherent in waiting for a request to be responded to. There may be circumstances on a busy WAN where sending large packets is blocking other requests and therefore causing poor response for other users.
In most cases, network performance problems in iProcess are not caused by the amount of data being transferred but the number of packets being sent. Therefore by increasing the value of RPCXFRSIZE many RPC calls can pass more data than before and therefore less calls are made. Even on a LAN a single RPC round trip can take 25ms irrespective of the size of the packet, i.e. 20 bytes or 4K, therefore 200 RPC calls are likely to take 5 seconds. If by increasing the packet size only 50 RPC calls are made then the total time come down to 1.25 secs.