Bushwalk Australia

The Canyon season is upon us again!
I did my first canyon of the season and I had my goretex raincoat on to block the wind we were getting and also for some more protection going down the wet abseils.
I got to thinking how I didn't really need a breathable waterproof layer because hey, I'm already wet. I just need something to stop the waterfall running down my neck and block the wind.

Was thinking of making a vest out of PU Cordura. I'm very new to this so wanted to check my maths before I order. I'm guessing that my torso and had would be 3 ft and I'm about 1.5 ft wide. If I order 6ft by 2ft of 8oz Cordura will I have enough? And are my maths right when I say that piece of fabric will weigh about 450g?

Anybody made anything like this before that can offer some advice?

Better to get more fabric than run out but why such heavy cloth?
If stopping the water running down your neck is a priority perhaps a hood is needed?
It is a long long time since I did any canyoning ( although we called it Liloing then) but most of the people were wearing thin wetsuits with heavy weight nylon/cotton boilers suits over the top or just shorts when the weather was warm. I don't remember any-one ever wearing PFDs or helmets. So why not just a cheap proofed roadworker style jacket and cut the arms off??

Thanks MD.
Good point on fabric quantity.
A good hood sounds like a great improvement. Idea behind the heavy cloth was to be pretty durable as sliding over wet sandy rocks tends to be pretty brutal on clothing and gear.

Certainly don't wear pfds or anything to bulky but I do wear a helmet so will have to that into account. Hmm..