To echo the above, the part you're taking on should be relatively straightforward to mould, but just plan carefully and be as neat as you can with your outer edges and give yourself at least 4 inches of flange area all around. Steep transitions from part edge to flange can leave you with areas prone to bridging, so use plenty of wax etc. to smooth this out

I'd recommend using the Unimould system over the epoxy gelcoat/resin option, as it's much more forgiving and easier to make good any areas of imperfection, which you might get on such a large surface area

I totally agree on the point of large flat/simple shapes being much easier to do ... but also much more expensive when you get them wrong..

I started out trying to make very small, rather complex parts, since I had access to small laboratory vac pumps and not much worktop space..  I did not make successful parts for the first 4 - 5 times ..

I then did some tries "totally simple" and made some medium sized flat panels and very simple "bowl -shapes" (for Sub-woofer -membranes)  This was all wet-lay in the beginning, but with vac-bagging ..  and very successfull .. But you do not learn from doing the easy stuff .. so I started reading and trawling all the composites forums and looking at the *tube --

Then I went back to the small complex shapes /moulds, and tried again ... with much more success

Then I went "skinning" ... And found it quite difficult and a lot more work to get a "shiny" result .. Then I bought a bigger pump and some time later the "infusion kit" from EC .. And that really got me going ..

On top I started experimenting with steel and aluminium moulds -- milled from stock .. and doing what some people call "forged carbon"  for smaller parts .. with varying success ..

I would think that a large bonnet like the one from an Audi A5 is quite a big one to take on as "a first"  -- I would hesitate a bit even WITH my current level of experience to be honest ..

Infusion would be the method of choice, but that process does not get any easier with bigger size ....

My biggest pieces have been bike tank covers and fairing panels .. They were not difficult at all ..  And still I had a few "fails" with parts that had tight corners  .. trapped air .. bubbles, poor cosmetic finish .. bridging --

"Sapere Aude"... Dare to KNOW!

The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...

103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)

i did a boot for my first attempt including infusion! So don't be shy, I would start with a smaller part first though to limit costs on the first few attempts that go in the bin