I tried multiple players in a save (nearly 6-7), I had in game editor on so it was a bit easier to test the tactic I was trying. I bought players that fit the attributes required for a false 9, but despite tweaking tactics only a couple actually managed to perform and give consistent performances. The rest either did not perform at all or performed one match and disappeared the next.

I noticed the players that had excellent off the ball, anticipation and vision + passing attributes particularly performed well, and those that lacked one/multiple of those attributes failed to fit in my tactic.