That CG formula you quoted
CG [in % back from the wing's LE] = 16 + (36 X Tail Volume)
is for regular monoplanes. So is the even better one I use
CG [in % back from the wing's LE] = 10 + (40 X Tail Volume)
(That one is better because it gives better CG's for a wider range of aircraft, especially WW2 scale types).

This is far from a regular aeroplane. It has 3 wings and lots of rigging wires so the assumptions used in making up the formula are no longer valid. This aeroplane will have more downwash over the tail and there will be a greater loss of dynamic pressure (airspeed) over the tail.

Therefore the CG has to come forward to 20% to 25% of chord for in itial test flights at least.

Alasdair