I've had some good success making resin infusion motorcycle body panels for my project thanks to easy composite products and videos, but am now moving on to the saddle for the bike that has to be structurally strong enough to cope with a 100kg rider and all of the forces a road going motorcycle experiences. I'm borrowing the seat design from a Ducati supermono where a CF saddle structure then has a light thin cowl fastened over it to complete the overall looks and aesthetics. It's on the saddle part that gets the forces applied. I've been lucky enough to have a quick examination of an original Ducati part and it appears to be only 5mm thick pure CF (autoclaved pre preg) with four bolt mounts at the front, two each side the same as I intend fixing it. The rider is therefore exerting the down force on the seat at the opposite of the saddle to the mount points, I.e. greatest pivot effect. I was surprised that the original seat, a pure racing item likely to be subjected to far greater forces than a road bike, was only 5mm thick.
I had originally expected to have to make something about 10mm thick to work but perhaps I'm over engineering the part. 
My plan was 2/2 200g twill for the top surface to visibly match the other panels then 2/2 twill 450g cloth in reinforcement, probably 6 layers. Do you think this would give me the structural strength I need to sit on it? Should I use fewer or greater numbers of 450g layers? Would I be better off replacing some with 2mm soric as a sandwich? 
I'm still finishing the plug before tool coat and moulding but would wanted to plan it out so any advice would be appreciated. Some ongoing pictures of the plug are attached, you can see the mount bolts in some of them. Look forward to your thoughts. Thanks 😊

Thanks Warren, I'm going to use soric in the seat flat area and I'll do as you say on the brackets either side. It'll be interesting just trying to get it all in the mould.  I know you can use soric without infusion mesh but in that case inpresume it has to virtually go to the edge of all areas of the part does it?