Just scored used 9x28 New Deal. Only came with the original 4.6" infinity center fin. Had an old set of plastic T1 5.14" sides that I put In. 1st good session in chest high waves was a blast! Pretty much caught what I paddled for and really like it. Looking for advice on fin setup for waist to head high. Looking for performance, fast down the line speed with control/drive to do big cutbacks. 5'8" 160lbs 72.5kg
really appreciate any shared knowledge here.

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firesurf said..
Looking for performance, fast down the line speed with control/drive to do big cutbacks. 5'8" 160lbs 72.5kg

Now that's super easy: Quobba fins M
There is no other choice :-) The added speed is especially noticeable on cutbacks.
quobbafins.com/collections/dark-glass-series/products/dark-glass-series-medium-single-tab-thruster-set

Take the glass ones above if you want a bit of flex for speed and a fluid drive, my favorite for boards with thin rails like I guess the new deal
Better for horizontal surfing, e.g. big cutbacks.

Or the carbon glass, a bit stiffer, if you want a more positive feel when pushing hard on them.
Better for vertical surfing, e.g. smacking the lip
quobbafins.com/collections/carbon-glass-series/products/carbon-glass-series-medium-set-single-tab-thruster-set

Do not take the large ones, at 72 kg you do not need them. At 97kg I use the glass M myself for my "cutback board".

Looks like to make the Quobba thruster set work would require the FCS LONGBOARD BOX ADAPTER.
would need the 2 medium sides in futures (single tab) and the Center medium fin in FCS to fit center box adapter.
Those Quobba fin's do look interesting. Glad you shared proper size and benefits of the dark glass.

Yes for the adapter. Do not hesitate to email the Quobba team if you want a specific order (e.g. future sides + fcs center)

I use the FCS adapter in my boards with a center US Box.

Quobba fins work by reducing the interference drag at the junction of the board and fin.
Like fairings and fillets for aircraft wings.

And since multi-fin setups (thrusters and quads) create a lot more interference drag by multiplying the fin/board junctions, and having a much bigger board/fin interface relative to the fin size than for single fins, this is all the more useful.

The fcs adapter is a good idea. I found the stock fins were a really good match for the new deal. The fronts are actually bigger and more upright than quobbas, probably closer to what you have in it now. I recommend www.k4fins.com/product/surf-sup-wave-fin/ in size L for fronts and then a smaller 4 inch fin in the rear using the fcs adapter, something like the fcs m-3 or quobbas med probably works. Or if you are trying to nose ride keep your stock rear fin. I found the new deal worked with many different fins from twin to 2+1, but I liked the drivey feel from the bigger stock fin set probably the most and it still turned great.

Ending up going with the Futures F8 Blackstix.
Had the infinity center fin which is about the same size as the sides. Should see some surf this week so will see how it goes

I liked the stock fins enough on ND that I never switched, it wasn't loose in smaller surf but I use ND in solid days, to go fast and do cutbacks, stock fins great for this.

At least a dozens sessions on the 9x28 ND now .
love it! Thinking the F8 Blackstix sides are close to what came stock although have maybe more flex.
Very Fast down the line, very easy to pivot and cut back stepping on the tail. Found myself stumbling up to the nose, and nose riding is my challenge. was split between getting the Blackstix or the Quobbas, but was able to grab the Futures set at local shop for good price. At some point will pick up a set of Quobbas