Lately I've been riding a 5'9" Chemistry Tron, but I'm looking to get a more traditional shape shortboard for bigger and steeper days. Around what size range would be a good fit for me?

I'm 5'10", around 165 lbs. I'd probably classify myself somewhere between a novice and intermediate surfer: off and on for several years, good paddle strength, can bottom turn, ride down the line, and catch waves consistently; starting to try cutbacks when I can with some success. My recent relocation near the shore has gotten me back into surfing 3-4 times a week year-round if waves permit, so I'm making a strong effort to get better every day I go and want a board that I can grow with for a while.