Help fitting A5 seats in 3dr 8p

[AudiLeon96]

So recently I managed to source a set of full leather S-line seats from an A5 coupe for £150. I've been able to fit the front two by grinding down one locator lug on each side (pics of front seats below)

Don't worry I've already been flamed for my taste (or lack of it regarding the white Centre console, it'll be changed soon)
I'm having a real hard time working out how the rears go in. I remember reading something about this claiming that the actual backrest needs to be shortened but it infact is the correct height to fit in by the looks of it, it seems to be getting stuck on a square(ish) metal piece just underneath the bar on which the seat tilts on, (pic below)

Now can I just grind this piece off to fit the seats or will the loss of that piece be detrimental in some way, I just want these seats in so if anyone would be so kind to shed some light on my situation, I'd be very grateful.
Thanks in advance!!

 

[LEE69]

Isn't that the isofix point for child car seats?

 

[AudiLeon96]

I really don't know what it is if I'm honest, don't know whether it's okay to grind it off or if there's another way to fit the rears in without grinding it, I just don't know, and the problem with this piece is once it's gone, it's gone, I can't exactly buy that bit and put it back on ya know, sticky situation for me if I'm honest.

 

[LEE69]

If you have 2 sets of them then yeah isofix. Depends if you need child car seats, or the next owner.

 

[AudiLeon96]

Just had a look and it turns out there are two of them, so I guess you're correct about it being the isofix points. I infact don't need these at all but ofcourse cannot guess whether the next owner will need them or not, but it seems to be this isofix point that's stopped the rears from fitting in if I'm not mistaken.