DIY RPG Bad Flat Panels Basic Questions

I finally got the binary sequence CNC'd. 4 of 120 by 60cm. 2 positive and 2 inverted with 12.7mm diameter holes.

Unfortunately the only nice laminated bench tops MDF's were in 18mm, I am aware the Bad panels are usually 9 or 12mm thick but I don't think that will cause any issues.

The other thing is that I will be placing them over my current panels, which won't give the same low frequency absorption but still provide enough absorption under the 1000hz mark.

I want to place one front wall and one back wall and the other two in direct line of fire of my horns. The horn speakers are toed in and the line of fire will be the opposite side wall.

Does it matter which location I use for the positive or inverted panel?

Also the orientation does it matter?

And any other advice for placement?

Of course measuring is best approach but once I've added them it's hard to change so I might have to go with the stick and leave it approach. So any recommendations will be appreciated.