Personally I think an 11'6" would be too big.
I started on a Coreban Rockett 10'6". I am 90kg and 5'7" (not sure what that is in metric). The Rockett is great in the size waves you describe but is also used by my wife, 10 year old and 8 year old. It is also fun when you just go for a paddle because there is no swell.
Check the Coreban boards out at ->
coreban.com/Try and demo one, if you can.