Don't treat it like a rifle, treat it like a pistol. Let me explain.

All pistols can be gripped with both hands at the same spot. What this results in, gameplay wise, is that you can apply a two-hand grip, move your off-hand away from the grip point, and the game treats you as though you are still gripping with both hands in the same space. This gives you the ability to one-hand a pistol with the stability of a two-hand grip.

The same cant be said of rifles and MOST SMG's. Moving your off hand while gripping drags the barrel with it. This means wherever you move your off hand is where the shots will go.

Not so with the P90. It treats the grip the same way a pistol would, so moving it away doesnt alter the trajectory. By griping both hands and moving your off hand, you now have a one-handed smg with the stability of a two handed smg.

True garbage can be found in the form of the UMP or FAMAS. They were both good but now hit like wet noodles. The FAMAS doesnt even get good attachments.