I've made a few parts for my motorcycle project using vacuum infusion and the products available from easy composites and am moving on to the seat now. I need to make the seat pan between 10 and 12 mm thick so it is self supporting, I.e. no metal subframe. The items I've made so far probably peak at 4mm thick. Can I make a 10mm thick part in a single infusion or is the technique to get to 10-12 mm thick achieved by running successive infusions of smaller thickness? Grateful for any experience people might have on making thicker parts.
Thanks 😉

Thanks for all of the responses guys appreciate it. I might not have explained the requirement too well and I'm still a bit early in the plug making phase to be able to post a photo that will help withbthe explanation. The seat is a basic pan shape, maybe 10 x 8 inches with two forked prongs on either side that will bolt to the frame in the front. It has to withstand the forces of let's say a 120kg rider sitting on it acting as a lever on the front four bolts, plus the additional forces created through suspension travel on a normal road. 
I've looked at a similar design today on another bike and the carbon seat pan is about 6mm thick so maybe my 10mm estimate was a bit on the high side! 

If I aim instead for 6mm, I presume I can do this as one single infusion of several layers of cloth, would you agree?

I understand what you are saying about steel plate Steve, but a steel alternative to the shape I need will weigh a lot more than the carbon version plus will add complexity with the seat cover and other items in the design so steel really isn't an option for me.

I'll see if I can take a photo of the plug so far that will illustrate better what I'm aiming for...