That ebay item sits on the glass....not on the roof.

As with any fiberglass piece...the mold it is made from is good for only several times....then the mold starts to warp. You probably got the warped one.

I say spend for quality parts that fit correctly. I've been in your shoes before with my first roof spoiler (DSR v2)...and had fitment issues. I sanded it...and sanded it...to the point where I wasted time and money to make it fit....NOT worth it.

Good luck.

Pete