I am wondering if it would be ok to cut this piece out to fit a big 6.5" magnet.

I have shallow mount polk DB651's but they lack in power and quality.

I measured the depth and the magnet will not hit the window motor or any parts of it when it goes up or down.

This rubber piece is the rubber case thing for the magnet.

On a side note, why the hell are the rear doors so nicely sealed compared to the front doors?

 

Hmmm, passenger comfort? I dunno, but there's no good reason why vehicles have to be so noisy in the first place.

From what I can recall the last time I had one of those doors torn apart there's no good reason why you can't cut that out. It won't affect the structural integrity enough to amount to a hill of beans. So as long as it doesn't affect the window articulation then I say go for it! What do you have planned for the cheapo factory plastic mounting ring, replacing it with an MDF ring?

 

Well apparently the 2 bolts you see are actually part of the window motor guide and can't be cut.

But luckily there is enough room between the speaker and grill that you can make an MDF ring, which I will do eventually