Carpet underlay

Having stripped out the old torn carpet from the TF after removing the tunnel, console & cubbies Im unsure what to do about the underlay. The replacement carpet from Mgfntfbitz has the left and right side joined and includes an integral underlay whereas the one I have just taken out was just a basic thin gel backed carpet with no integral underlay and with the left and right side separate. From what i can gather that must mean Im replacing an aftermarket carpet with an original OEM one,

There are thick felt underlay sections in the footwells and behind the raised section of the seat support, really thick felt that will readily absorb and retain water by the look of it. Are these actually factory original that would have always been in place under the original thicker carpet or are they just something that would have been supplied with the thin aftermarket carpet to pad it out from the floor ?

When the cars were made was there an extra layer of underlay like that or was the manufacturer's carpet with it's built in underlay just fitted straight onto the metal floor ?

Hi
There’s a TF carpet upgrade bit in the how to section full of pictures that may prove useful..

I read the 3 articles on carpets in the How Tos but they dont mention what is supposed to be in place.

I would PM the supplier and get their feedback. Maybe they know or have experience of what other buyers do.
Surely someone on here has experience with this?
Personally I would just replace any underlay with a modern material anyways. I used aqua filter material one time due t9 it’s qualities and carbon impregnating to kill off smells. Worked a treat and water dissipates with the form and make up of the material.

I first assumed the underlay in the car must have been original as the felt sections were bonded to lengths of dense triangular section foam butted against the sills and other bits of dense foam padding This definitely looked mass produced rather than something after market hence the question about what is standard.
Not being sure what was original and what wasnt i separated the dense foam sections from the felt underlay and glued them to some sheets of closed cell non absorbent gym mat stuff in the same shape.
However I then found the 2nd hand original type carpet with its built in underlay also has built in padding in the equivalent places so i had to strip out the sections of dense foam before it would fit. It seems to be ok now. The carpet sits higher at the edges due to the thickness of the gym mat stuff under it so shouldnt pull away from the door shuts.