'glassing in my new grille - help, advice, idiots guide please!

[WorldClassAccident]

I think I have all the bits ready to fix my new grille to my 'long-nose' bonnet.

What I need is help and advice on the best way to do this so that:

A) It doesn't fall apart
B) Doesn't ruin the paintwork
C) Is quick and easy too much to ask?

I have the bonnet on a stand pointing nose to the ground
20170814_161123 by WCA!, on Flickr

From the inside you can see where the grille has to go. You can also see the white class I added about a year after I first got the car to deal with possible flexing.
20170814_161200 by WCA!, on Flickr

This is how the grille should sit - obviously the two brackets at the edges should be beneath the grille rather than lying to the side.
20170814_161253 by WCA!, on Flickr

The problem is that the nose is curved and the brackets & grill aren't.
20170814_161334 by WCA!, on Flickr

There are some fixed bolts that protrude from the brackets but only so far.
20170814_161415 by WCA!, on Flickr

So what do I do?

Do I make a glass fibre 'box' that has a curved edge against the body work but is flat on top so I can bond the bracket that?

Do I creates as above but have the brackets pushing through the flat edge of the glass so it is sandwiched between the bracket and the grill?

What prep for the bonnet before trying to bond anything to it?

Anyone in/near Southampton who has a clue what they are doing and wants to show me :-) ?

Thanks