I usually send my boys, who are GOS, off between 7 and 8 months. You get a reasonable sized rasher of bacon as well as joints, sausages and burgers etc. The whole boar into sausages would definitely be possible....a lot of sausages though.
Some people advise to send entire boars off by the time they are 6 months old because of boar taint. I've never experienced it though.