Technical '33 roof insert

The roof of my '33 5win has a groove formed around the periphery within which is a separate channel that once held the "fibrous material" into which tacks were driven. Does anyone know if this channel is attached solely by the rivets that also held the aforementioned material or if it is also spot welded in? Mine was potted sometime in the past with some god-awful rock hard, indestructible filler. I'd like to grind off the rivets from the underside and pry the whole channel out, but I don't want to tweek the actual roof doing it.
regards,
Phil

 

Pretty sure there was no spot welding of the tack strip to the tin.

 

Just rivets.

 

And the factory tar like sealer it's embedded in loosens with heat. I used a heat gun under the channel.

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We wanna see....

 

Thanks all. Confirmed there are no spot welds. It's really tedious grinding each rivet, exposing the top enough to grip it then working it out, but it can be done without damaging anything. Will post pics when complete.
regards,
Phil