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As the title says really.

I'm almost at the point where I will soon (probably this weekend) begin repairing the various rust problems/holes on the car. I'm torn between using repair/replacement panels from the likes of WallothNesch which obviously cost more but look far more factory (for example the floor pan moulding) and as such should require less fettling, versus using plain sheet metal which would require more fettling in some places but is ultimately cheaper, easier to source but just as strong.

So, based on that quandary, what's people's thoughts? Pro's & Con's?

I guess it comes down to how big the rust repair is. I tend to try and keep as much of the original panel as possible, as unless you're in a position to remove and weld in whole new panels to the same standard as BMW did, it's probably going to be more detrimental to the car than a localised repair properly done.

Good point. Most of the rust repairs I've encountered are small, no bigger than 4"x4" (inches). The worst is the drivers floorpan/footwell, this section is approx 12"x8" in total once I cut back to solid metal.

My point with the repair panels was that in the example of the drivers floor pan area, I would have cut the whole section out and replaced to make as "factory" as possible. I'm starting to think this is overkill (perhaps) as the floor will be covered with carpet and sound deadening material anyway so never seen.

Here's a quick mock-up of the difference between the sheet metal size and repair panel cutout:

why not use a section of the repair panel rather than the whole panel??
advantages are:
proper contours like new,
just as easy to weld in like plain sheet
easy to trace and cut to size as it will just sit right over the hole after cutting out all rust.

That's a good idea, not thought of that. However I'd feely slightly peeved at paying £125 for a repair sheet only to cut it up and use a portion of it.

Another point I forgot to mention was that the previous owner had chose to cut out the passenger floor pan in favour of plain sheet metal for similar repair. So if I do the drivers floor pan with the correct repair panel I'd feel compelled to cut out the passengers and do that all correctly.

I'm prepared to do the work, in either way. Question is, would it be lacking in detail or attention if I went down the plain sheet metal route?

I suppose it depends on your end goal for the car the quality of the finish.

I wouldn't think twice about cutting a repair panel, especially if it means leaving OEM spot welds, joints, seam sealer untouched. as long as they are sound that is.
Then whole panel to ensure no rust between spot welded flanges.

I would always cut a repair panel to minimum to complete the area, if any future repairs are required e.g a rear arch gets a shunt, then the future repair section can be extended to fresh OEM metal.

keep your eye on ebay for old stock sections.

drift/rally/ race or daily dog, buy a deep throat swager for 150 and set of panel hammers then flat sheet the lot.

Fair point. I'm not going for a concours finish and the plan is certainly for more of a weekend toy/fast road/track/drift car. Currently I'm swaying towards a stripped out lightweight road car.

I'm also looking at coating the interior with the lizardskin type spray on soundproofing. Think I'm decided on repairing with solid sheet metal for a smoother seamless finish as there will likely be no carpets.

Probably worth reading/commenting on my main restore/mod thread as more details and pictures in there:
viewtopic.php?f=53&t=24739&p=266620#p266620