What to do about corroded body tub mounting holes

I have been meaning to post this for a while, but only got round to it today.

When I removed the rear tub, I noticed that the area around the mounting holes was corroded away, leaving more powder than metal.

I have access to offcuts of aluminium sheet in varyitng thicknessed. Would It be strong enough if I was to cut out the corroded bits and pop-rivet some replacement pieces of sheet in? I would think that an electric jig saw with the right blade would cut through it easily enough.

Here are the holes that I am talking about. The rest of the tub seems to be in fairly good condition.

Thanks for any info.

You would be better of leaving it in and adding a plate across it , the corrosion can I believe be removed with some vinegar just make sure you wash it all off afterwards and give it a lick of paint.
How to dissolve corrosion on aluminum | eHow UK.

I cut it out and welded a plate to replace it (well I got someone else to do it as I can't weld ali with the welder I've got)

I'd plate over it but use nuts and bolts over pop rivets for extra strength....not sure what an aluminium rivets tensile strength is like over an 8.8 grade bolt