Way back in 2004 when I built my -8 from a Quick Build kit (wings and fuselage), the tanks came attached to the wings, and I never once took them off - didn’t need to for fitting wings to fuselage, or for anything else for that matter. Just checked the torque on all the Z-fitting bolts, and moved on. 2090+ hours later, they have never been off.
That’s just a data point for the OP, and I can’t speak to any differences between the -8 and the -9….. but the same thing was true for the QB wings on our -3…..
Paul