Good to watch your very comprehensive build! 
 I used a building industry product called Ametlin for the hood lining on my Puma. You can get it in 4mm or 6mm, I used 6mm, which is equivalent to r2 insulation batts plus you've foil backing both sides to reflect heat/cold. 
It's flexible, non adhesive and I didn't remove the lining to install it. Just opened the lining at the join and slipped insulation in, folded double at the edges for easy placement, then unfolded it once in place. Made it a tight fit and it sits on the lining, trapping the air in that space - air being a great insulator. 
It made a huge difference, both in summer - keeping the heat out, and in winter - keeping the heat in plus, it was so easy to fit. 
I also used it, in conjunction with sticky Velcro dots, to make removable panels on my awning window and other windows around the fridge and on rear window where we kept the water cooler. 
I dynamatted everything else. 
That was then, this is now; the puma's gone and I haven't done any insulating of the td5 yet! 
I do have the front vents though 

The to do list is ever present
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