Hey guys! This will be my first post

I'm an acoustics noob so please bare with me.
My mix position seems to be in the peak of a standing wave at around 130Hz. If I play a 131Hz sine wave while sitting, it's quite a bit louder compared to other frequencies (C notes stick out like a sore thumb) and when I stand up it almost disappears. If I stand on my toes I can hear it again. It's because of this I've come to the conclusion that it's an axial mode between my floor and ceiling. My ceiling is roughly 2.5m high and the width of the room is roughly 4m.
I don't have any bass trapping in my room at the moment (other than a queen sized bed in the back corner and 2 small couches if that counts) and I'm thinking of building two panel bass traps from rock wool and hanging one from the ceiling above the mix position and one closer to the front wall at an angle.
Am I in any way going about this the right way? If so how thick is thick enough and how much space between the trap and the ceiling is space enough?
Thanks in advance to any replies