I recovered a dashboard for a mechanic that is a new customer to us. The shop accepted it and commented that it looked great. Someone before had attempted to fix it and sprayed and put superglue in the old cover. The shop said it looked better than when it came in. Their customer doesn’t like that the seam is raised. I did it the same way they with a flat reinforced French seam.
I think that if you used a layer of 1/4 landau top pad over the whole surface if would allow you to sand it and eliminate a lot of the bumps.. You could also cut a channel in the foam where the seam lays and that would lay the seam flat.
To me it looks like the dash wasn’t cleaned up enough before the close cell was applied or when fitting the cover was lifted a few times with glue applied. But to answer your question I wouldn’t let that go BUT was it cheap or top $?
In my opinion reinforcement isn't necessary on the french seam on a dash cover. The cover is stuck to the dash and supported by it, so once it's fixed in place it'll sit there happily. That would reduce the amount of material beneath the seam.
There’s absolutely no need use backing tape on a dash, if the leather shrinks due to heat no “backing tape” will help!
When you stitch a seat base together which takes the biggest loads do you back it?
Agree with my pal Gareth on this ☝️ To this day we have never used backing tape on anything. I’ve seen jobs we’ve done that are so old (15+years)the Leather has worn through before the seams have split in high use seating, let alone dash panels that are bonded and little to no stress.