Installing the rear carpet has to be nearly the most frustrating job in this 2.5 year restoration of my '68 convertible. What a pain. So, I have about 10 questions, but I'll focus on the top 2.
1. The fitment of the ACC carpets from Wilcox isn't even in the right ballpark without some serious trimming. For example, the lump I assume to be the front of the wheel hump is about 4 inches too far forward and 6 inches in from where I would guess it goes. So I can hack material off of either the back or the top or both. But getting the edge contour right when removing that much is going to be really tough. Is it normal to have to make huge changes? I know everybody's advice is "use the old carpet as a template" but the car didn't have carpet. Also, I'm not sure how it was supposed to fit in the first place. Does it tuck behind the spring or go in front? Does it go all the way behind the rear door post? Am I supposed to notch for the latch on the deck lid and tuck the rest up? Any suggestions for this would be greatly appreciated. Also, I am using the ACC jute as well.
2. For the big flat piece in the rear, it looks like a flap is supposed to go in front of the springs, but then the rear deck arms fold it all up. See the pic. I can't imagine this being right, but don't see another way.

 

I agree it is very difficult, you will have to trim that piece - But I recommend installing the sides first. I have done my carpet 3 time now over ~15 years (sadly it seems to fade pretty quickly) ... fortunately I had the old carpet to get me in the ballpark. For what it’s worth I have the old carpet out of my 69 coupe. I can pack it all up and ship it to you if you want to pay the shipping - no guarantees on me having done it “right” ~ 5 years ago though...

 

The piece in that first picture has a finished edge, so I don't think it's supposed to be trimmed. And, yes, I'm installing the sides first. I was hoping that putting this "easy" piece in would give me a clue about how the carpet goes around the springs, but it just created more confusion... I might take you up on your very generous offer if I can't get it figured out. Of course, I'd pay for shipping and your time. I'll let you know.

Here are a couple pics of the side pieces kind of shoved back where I assume they'd fit with respect to the humps. Does that look like an excessive amount of trimming?

 

Hi EM,
"2. For the big flat piece in the rear, it looks like a flap is supposed to go in front of the springs, but then the rear deck arms fold it all up. See the pic. I can't imagine this being right, but don't see another way."

On convertibles the rear bulkhead piece of carpet had the 'tabs' on each side glued to the side of the deck lid hinge bracket.
This actually turns the carpet back towards the front of the car and creates a 'slot' for the hinge to go up and down in.
Regards,
Alan

Form the 'corner' where the lower arrow indicates and glue it to the side of bracket as the upper arrow indicates.

 

Ah, that makes perfect sense. Thanks! It's that kind of information that I figure I'm just missing for both the carpet and my other post about the rear quarter installation. I wish I had a local guy with one of these so I could just crawl around it for ten minutes. It would save a ton of headaches...
Alan, you are an invaluable resource.