Ford Puma rust on stills?

As others state, welding in new material is the correct way to do this type of work. You can make it a whole lot easier by buying new panels either from Ford (if they do them) or from the many specialist body panel firms. Its so much easier than trying to fashion them from sheet steel.

As a point of interest, my brother exported a 1985 Rover 2600 Vanden plas to South Africa in 1990 when he emigrated. Several years ago I sent him a complete floor pan (genuine Rover part) as the inner sills and footwells had holed due to corrosion. The part only cost £145 , it cost £300 to send it and the South African customs charged him almost £300 import duty ! They say we get dafter as we get older....!

Cutting out the rotten sections and welding in new is the correct way to repair it. If it's done properly, then you have nothing to fear from the MOT man. It's bodged repairs with rust covered up with filler or fibreglass, or panels put in with pop-rivets, or rust that hasn't been repaired at all that they are on the lookout for.

A word of warning though, if you haven't got any experience of this sort of work, then don't try it yourself, at least not without help from someone knowledgeable. It takes plenty of experience to master how to repair bodywork well.

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If you do a decent job of it, welded sills are fine.