4096 is a good goal, but there is a much more obvious benefit at 1024 since it would fit within the IPv6 1280 MTU (i.e. a single packet). I recall hearing stories that the Google Homepage had to fit within 512 bytes for IPv4's 576 MTU.
One packet is great if you can do it. There's a big penalty after the sender in a new TCP connection reaches the initial transmit window. A lot of sites these days have configured this up from 2x or 3x MSS to 10x MSS (about 5,360 bytes) to increase what can be sent in the first transmission back from the server (HTTP response for example).
