Don't want a soundpad in my enginebay,is it simply enough to fit it behind the seat backpad with out compromising how that fits?
Material I have is around 5mm thick,backpad not out yet so just asking in advance,

I lined my rear interior firewall with Dynamat and placed the stock molded rubberized pad over the dynamat. I used spray contact cement to hold it place.
The backpad went back in without difficulty.
Hope this helps.

The lower pass side of the engine compartment pad, If that's what you mean, might be loaded with battery acid residue. Moving it to the interior might not be a good idea.

I took the heavy stock rubber pad off the interior side of the car and will replace it with a modern dynamite/fatmat type pad and then the stock foam and vinyl back pad. No engine side pad will be used.

Under the rear carpet is good too. Sound bounces off the pavement.

Most take the stock rubber pad from the engine bay and.....throw it in the trash.

There's quite a few on here that have lined their complete interiors with dynamat/fatmat with stated success.

Cars a -6 conversion had no intention of using enginebay pad anyway,dyna matting the whole the interior is not my thing too much weight added,I don't want the car heavier and have removed weight where ever practical.
Cheers for the comments sounds like it will work for me.