Style bars, fitting to parcel shelf

Hi all,

           i am a new member, and wonder if somebody could help me please. I have purchased a style bar from MX5 PARTS, the M shape, and i have fitted it to the car( 1.6 eunos 1992) by way of the welded side plates to the sides of the seat belt towers.Everything lines up and fits a treat, but what about the two middle plates of the style bar that sit on the back  of the parcel shelf. Having lifted the carpet and sound deading material i can see the panel, but have no idea what is underneath,( petrol tank,pipes?) If i do not use these plates, i will put another bolt each each side next to the other two. so the bar cannot swivel about a centre point.

Regards           Rayboy