6'8" Rusty Blackbird is a perfect stepup for SD/Mex. Paddles great. I got mine last winter after being way-undergunned during that massive DOH December swell at Garbage in The Cliffs. Got tossed around and had one of those panicked moments where I truly regretted being out there on a 5'11", and said never again.
I took my 6'8" out to Ab on that swell. Sets were hitting south of the main peak and way outside in the DOH+ range and cranking on through. A lot of people learned the "foam is your friend" lesson the hard way that day. I saw about 25 people make it into what they thought was the lineup, and 23 walking back up the trail with barely-wet 6'0"s and tails between their legs ten minutes later. Two of us made it out to the actual peak: me and a kid on an 8'0". I was the only one that caught anything and got a completely solo session for most of the afternoon.
Even the 6'8" could have used some more foam. I would have been happy with a 7'0" or even 7'4-7'6". I got washed through a couple times and had to paddle back out from the channel south of Newbreak.
I was stoked until I heard that some of the LJ reefs were all-time that day and I made the wrong call.