How about some pics of the top corners?
The problem you have now is if you move the bonnet down or forward it is going to foul the slam panel. It also looks as though the front of the bonnet doesn't follow the curve of the top of the bumper.
I will try to remember and take some pics of mine tomorrow.
Here's one which shows the line of the bonnet and lights. You probably know this, but it might help to compare it to yours. I have since altered the slam panel on the nearside (with a hammer) to make it fit better.
It looks as though the front of your bonnet is too flat.
Take a straight edge and lay it across the front underneath of the bonnet, where it meets the bumper. There should be a gap in the middle where it curves away from the straight eddge. Measure that gap. Now do the same with the bonnet you took off and compare.
It looks as though the very front of the bonnet is hitting the slam panel too early.
If you push down gently but heavily on each side do they line up or does it feel like and obstruction. If they line up then you bonnet may be slightly distorted.
Remember, when the panel was fitted a lot of the strengthening beams would have been cut away and the bonnet will flex a lot more. The vent that has been blended in may be flat rather than curved like the bonnet and may be causing the sides to lift.
This is only speculation as it is difficult to diagnose from afar.
If this is the case you could see a bodyshop and see if they can put the bend back into the front of the bonnet, or you could fit bonnet pins at the corners which would effectively hold the edges down inline with the wings.
It looks as though the front of your bonnet is too flat.
Take a straight edge and lay it across the front underneath of the bonnet, where it meets the bumper. There should be a gap in the middle where it curves away from the straight eddge. Measure that gap. Now do the same with the bonnet you took off and compare.
It looks as though the very front of the bonnet is hitting the slam panel too early.
A lot of strength is lost when these conversions are done. If the bonnet was transported on its back etc it may have "flattened out" a bit.
If this is the case then all is not lost as it should be fairly easy to bend it back into shape, but be very careful and gentle as any filler etc around the vent will not be flexible and may crack.
I would investigate everything else first.
From the pics though it looks as though the front of the bonnet has already met the bumper and could not go any further, yet the outside edges have some way to go, this is how I came to my conclusion.
The only other possibility is that your slam panel is too curved, but I cannot see how that could have happened, so the bonnet is the suspect.
Is there much flex in the bonnet? Is it more floppy than the other one?