T-top for 18' SC

[rayhawk]

I am looking for advice on t-top size for a '78 18' boat. I have looked at other boats and a lot of people seem to go with a 5'x7' size, right now I have a 6' long bimini top and it does seem a bit short. Anybody have this boat, or the 20' please give your opinions on sizes that you have on your boats. I want decent sun coverage but I dont want to overdo it for the size boat.