Best method to fix new pannier clips to old Karrimor bag

The original clips on my Karrimor bags won’t fit a 12mm rack

So I bought some other clips to see if they would work

The original clips (red coloured) have grooves in the plastic that kind of clip into the rail on the bag. Then you simply screw a small screw in

The replacement clips (blue) are a flat profile.

What do you think the most secure method of securing the new clips onto the rail might be.

There isn’t much space behind the rail btw. (I’m not sure a bolt would fit behind)

I’d put a washer on it and a screw with a corse/self tapping thread.

or drill the rivets out and replace the whole rail assembly with a replacement full kit, you can buy Ortlieb ones.

https://www.sjscycles.co.uk/luggage-hooks-fittings/?brand=rixen%5Fkaul

Did the same swap and I think I used the self tapping screws in the above link.

drill the rivets out and replace the whole rail assembly

I ended up doing this to refurb an old pannier. Worked perfectly.

Would a self tapping screw be strong enough. I know that’s how the original clips are fastened on but they have a ridge in the plastic that also kind of clips into the rail.