Yes, you don’t want the neck in the pocket itself. 25.5” scale length. It’s on the kit info page. The intonated position for E4 will be very slightly longer by maybe 0.3 to 0.5mm.

As I mentioned in that other post, check the saddle positions on the bridge. Use the high E4 string position to measure the scale length (nut ‘slot’ to saddle). If necessary bring the high E4 saddle as far forward as it will go to achieve the scale length (though I prefer to have it slightly back from fully forwards if possible when setting bridge position, but in this case it’s the neck that can be moved but that is very uncommon). Ideally the end of the neck should go level with the pocket edge, so as the bridge post holes are pre-drilled, you’re really seeing whether the saddle positions can be adjusted to suit.

You might need a mixture of cardboard supports, tape and blu tac to hold the FR in place so you can measure scale length accurately.