I've been working on a calculator that uses the Tail Volume coefficient to find the NP location.
The calculator gives both the wing area and the stab area, so you don't need to calculate it, just measure the plane and type in the figures, no math needed at all.
You also get the CG location by entering the Static Margin you want (typical between 5% and 15%).
You may check it here https://rcplanes.online/cg_calc.htm.