Ya the plywood isn't very slippery at all, but worked for what I was doing that day. I'll try some counter top stuff next time when I have to cut some shapes. I see people use band saws too but that would just be something else taking up floor space, this thing folds up and away as it is on a saw horse thingy for glass.

Tacking strip is the card board stuff ,I meant.

You will have to replace the tracking strip to hold the windlace but usually you can use the normal metal door panel clips on the sheet metal behind the upholstered panel. Just try to get as close to the tackstrip as possible and use a stiff product like 1/8 mahogany so the panel won't bend from the clips being a little far from the edge.

Toluene is probably more correct for thinning but I don't have any tolulene, I have lacquer thinner lol. I use lacquer thinner for my paint gun or when I only have that one crusty glue brush that needs softening to finish a job, so it's always on hand and that's what the glue gun gets too.
I'm pretty sure any solvent that ends with "ene" is really bad for you too.

Ditto on what Jack said. Even with doing all of the above,
it will still be hard. You are at the extreme end of a regular sewing machines limitations and it's letting you know lol.
If you can find 210 size thread, it will be easier but I know it's hard to find suppliers.
Every time I tell a sewing machine tech that run 270 through a 206 consew, they say " whaaaat? That's totally not designed for that thread." Um ya I know, but it will do it, just slowly is all.
It's not just you.
You can use 69 or 92 for bobbin thread too but still slow.

Is it slow because of the thread?

10% lacquer thinner works fine for weldwood. It sprays finer for certain jobs that you need to have a smooth glue layer. I don't thin for carpet for example but do for vinyl. It just evaporates and has no ill effects.

Just say no. Sometimes those seemingly little jobs burn up a whole day.

Well done!

Funny! I've picked up a few things myself. I steam leather all the time but it's always been auto leather not fragile furniture stuff. I didn't know about sabaspray but options for glue are limited here and once a technique is figured out ,I haven't needed to look for something else. Saba spray would have been handy on that Maranello dash I did a couple of years ago lol.

I use size 21 for 69-92 thread and maybe 4mm for sewing and 5ish for top stitching

24 size needle is gigantic for normal sewing. That size runs 210- 270 thread. Regular sewing uses size 69 , I can't remember the needle size for that thread. I'll have to check.

I think the big problem is with large thread is that the knot underneath is too big and has nowhere to go, as it is too fat to go half way up the needle hole like 69 thread does.

I have an old consew 206RB that I use 270 size in. It's bottom load and works fine. I bought it new 20yrs ago and only use it for the 270 now since I have a new machine for regular sewing but the thread tension is set totally different for 69 thread.

On custom seat foam like the picture you have provided, you can use glue. I do it all the time, it provides a nice flat look like you see in finished custom jobs online. You can use the tufting string and tie it down too but it tends to look pulled in if you get carried away. Or a combo of both.
I know Gabes interiors uses glue too, I saw it on the interwebz so it must be true.

That was a veteran card.

This stuff. If you order in one gallon cans here, there's no dangerous cargo fees but if I order a 5 gallon can there is.
It still stinks but not as bad ,since I'm a glue connoisseur lol.
I always found helmitin had a fast bond time but always stayed a bit gummy and would let go on high tension areas. It was ok for carpet but damn ,you better be wearing a respirator inside the car lol.

One of these?
I forgot about Hydes ,they are good too.

Veteran Upholstery maybe?

The steaming just softens the glue again to make sure that it bonds well. Often the perfect glue timing can get delayed from positioning and fiddling with the cover to get an ideal fit ,so steaming will make it sticky again. Its not special glue.
Steaming also relaxes the leather to help it find it's new shape ,which usually gets rid of some slight wrinkles but will not make up for bad patterning.
As for glue, I've never really liked helmitin, the coloured glue can bleed through light vinyl and I found it never really bonded as well as weldwood landau top adhesive.
Helmitin stinks too lol , more than the others.

Ya dynamat is ridiculous, I'll check out second skin but usually options are limited where I live, if I don't want to wait 2 weeks.

Good to know Andy!

Regarding butyl sound deadener falling off, try spraying a light coat of contact cement first onto the sheet metal or fiberglass and let dry. The glue has to be well dried for this to work but it will never come off , ever.
I use Hushmat which is a little cheaper but works well for the money. Give it a try and see for yourself, it's a bit of insurance against the stuff falling off under a headliner in summer. ( not the Cobra)
As for carpet ,what everyone commented above is bang on. The Cobra carpet is done in multiple pieces like an English car with bound edges but has no compound curves, so whatever is stiff enough to be bound and can be bent over the tunnel will work.

That bar is an anti rotation pin for the tension plates. The thread doesn't go around it either, I see people do it all the time but it is incorrect. As William said , the plates will spin and Jim is right too lol.

How true Peter lol. Worn out bushings and linkage ends with no parts available, I would give the customer money to go away. That top was mediocre when new ,let alone now.