TLDR - Flyhawk appears to be under scaled
For this test, I've compared a number of Yorktown class waterline hulls. I've taken the numbers we have for the actual ship, and using the metric system, used my Tamiya hull to check my measurements against those of other members. As others have reported, they have found the Tamiya kits to be at a 1/719 scale. Measuring several difference areas using the cutting mat shown in the images below, I too found results in the 1/714-1/721 range. I measured the length at the waterline, max length of the hull, max length of the flight deck, length of flight deck w/o the ramps, and the overall length of the ship. Now that I have a method in measuring the approximation sizing of the Tamiya hull, I then measured the other hulls and the Flyhawk hull.
For comparison, here's are the 1/700 hulls we're measuring:
Tamiya Enterprise (width modified, but length as it came)
Flyhawk Enterprise
Trumpeter Yorktown (new tool)
Academy Enterprise
Tom's Modelworks Hornet (Resin, "replacement" hull for Trumpeter kit)
MENG Enterprise (Snap kit)
Trumpeter Hornet (older tooling, infamously known for its tanker hull)
Notes on measuring:
- Tom's Modelworks hull was advertised as a replacement for the Trumpeter Hornet kit, but it wasn't actually designed for the kit, but adapted for it. It wasn't a perfect fit, but its works with some modification, and makes for a great improvement. Instructions were provided on modifying the plastic kit to fit the resin hull.
- For overall length, only MENG, Tamiya, and Trumpeter Hornet could be measured accurately, as the hulls were built up enough for the flight deck to fit correctly. For the rest, rubber bands were use to hold the flight deck and hull together, placing the forward and aft elevators in roughly the correct position.
Here are the measurements, based in Centimeters, with comparison of the size of the actual Yorktown hull scaled to 1/700.

Based on my measurements, I estimate the Flyhawk kit to be around 1/715 scale. You can visually see how it compares in size to the Tamiya kit, which as stated above, its known to be under scale. Trumpeter and MENG seems to average very close to 1/700, with Academy just slightly smaller.
Some pictures to show the difference in sizing and shaping :
Here for the overall hull length, the bows are lined up at the 0cm line. Note that each hull has the same assigned number from the above table

Shaping of the upper hull to the waterline. You can see the improvement of more recent toolings since Tamiya and Trumpeters first offering

Comparison of the kits with full hulls with reasonable shaping. No idea why keel of the Flyhawk kit is so flat, that seems like an error. MENG's lower hull seems closest to the old Revell 1/480-487 hull, but I still think it thickens up too far forward. While not perfect, I think all 3 do a reasonable job of depicting a Yorktown class hull.

Comparison of flight decks

So regarding the new Flyhawk kit
Pros:
- Detail. While some might be inaccurate, the level of detail is incredible. Something you might expect from a 1/200 kit, not 1/700. The individual parts are quite detailed, and the number of things made as individual parts instead of part of a larger piece is very nice.
- Aircraft are probably the best you'll see outside of 3D printing.
Cons:
- Underscale
- Hull plating
- Hull shape is close, but it's still not perfect.
- Few aircraft. Standard comes with 3 each of F4F, SBD, TBD. Deluxe gives you a total of 6 each.
Despite its apparent issues, I look forward to building it.