Help needed with bonnet

[Enoch]

Hi folks, hope you are all well. I have nearly finished my build now, the only job left is the bonnet. My build uses the Twinky engine so the standard bonnet does not fit. No problem, I thought I will make an alli bonnet with a big old bulge in it. Trouble is I have no idea how to do it I have made several attempts at modifying commercial units, all I succeeded in doing was depleting my bank balance. Next couple of attempts were to make something out of a wooden former and cover it in fibreglass. More time and money wasted, the results were not good
Has anybody got any ideas or pointers as top how I might go about this? I am just about at my wits end. I really ballsed up on this, I made the scuttle higher than standard but the fuel regulator and cam covers are still way higher than I intended. I can't lower the engine as then I will have no ground clearance.
Any ideas gratefully received.
Enoch