Use 2048 bits, not 4096. I'm kind of paranoid and always try to use the highest recommendations, HSTS, all-SSL, etc. But in terms of SSL connection setups / second, your CPU will be the bottleneck, and having 4096 bits will limit you to about 1/4 of the connection setups / second that 2048 could have handled. So if the site has low traffic and a enough CPU resources, it could be ok, but if you ever need to handle a lot of connections: use 2048 bits! (I learned the hard way ;)