If the gap is where you've put the red line then it's caused by the lack of backing plate,

Look at this photo - this is a photo I took of just the backing plate on the car when I was putting my spoiler on ages ago.




As you can see it would filll the gap where the red line is because it fills up the top of the spoiler, you can get spoilers that don't require a backing plate (think they are copy ones) but I personally would just be looking at getting a backing plate.

[Edited on 16-07-2015 by Jason x]

It's at the bottom. That's a photo I took of it. Couldn't get one of it on the car but I'll try tomorrow. Basically if you stooped down and looked up at the spoiler when it's on the car, the red line is where the tailgate would be. As you can see the bottom of the spoiler sits out from it, causing that gap.

[Edited on 16-07-2015 by VoicelessGrapefruit]

Is the gap at the top of the spoiler?

Sounds like the spoiler might be misshapen after storage. It should line up. Brackets would help you out as per the GSi/Sport etc. tailgates but they're not essential.

I recently got a genuine GSI spoiler for my 1.2 Corsa B and it came without the mounting bracket. From what I hear this isn't much of an issue as the spoiler can alternatively be tiger sealed on, however when I lined the spoiler up on the tailgate to see if it would fit alright I noticed that there is a big gap between the underside of the spoiler and the tailgate. I'm just wondering if this is because it's missing the mounting bracket, or if the spoiler simply doesn't fit my Corsa's tailgate. Cheers.