Actually as I start thinking about it, minimum size is 28, not 46. Because this value includes both IP header (20 bytes) and ICMP header (8 bytes), it cannot be less than that. 46 is minimum payload size for Ethernet frame. If you are using only Ethernet for communications, setting ping size to any value less than 46 will not reduce traffic, as payload will be padded to minimum length anyway. However, if you are using communication channels capable of sending shorter frames than reducing ping size further can make sense.