You can use a rod over 8ft on a 6/0. In fact I like useing a longer rod for my 6/0, or reels about the same size.
1) you can cast them if it is too rough to yak, or if its night and you dont want to yak at night.
2)gives you more elevation over the water when the seaweed is there.
3) you can still land big fish on surf rods
here some pictures of fish that we have landed this summer on surf rods.
Here is a 7'10'' lemon shark caught on a casted trinidad 50 on a 11 1/2ft gander mnt. guide series surf rod. yes i know its not a penn 6/0, its a little smaller but puts out more drag.

Here is a 8'1'' lemon shark caught on a penn 12/0 mounted on a old school 10ft all star.

this is the 7'3'' lemon shark I caught this summer on a newell 646 mounted on a 12ft american rodsmith.

The 8'1'' and 7'3'' were both on yaked baits.