When I first saw this challenge I thought that the puzzles had to be found in consecutive weeks. Much too hard I thought, so I put it aside to try when I had more time.
I came back to it a few months ago and saw that I'd misread the conditions. So I fired up GSAK confident that I would qualify easily. However the conditions that remain are still quite tricky to satisfy. I've found loads of hard puzzles but some weren't allowed because they were challenges. Then there were many where I'd found them too long ago, and others where they had been published too recently.
As the numbers dwindled I found that I only had two possible days: Sunday and Monday.
Here are my qualifying finds all found on Sundays:
GC2RFKK Puzzling... by KnightFamily1980
published: 4 Apr 2011
found: 31 Mar 2013
GC1AMFD Eloise by Ian Too
published: 28 Mar 2008
found: 15 Apr 2012
GC4C35 Cuckoo Cache (could be anywhere) by The Wombles
published: 12 Apr 2002
found: 22 Jul 2012
We went to collect the cache this afternoon and it was an easy find. The log is absolutely soaked though and I could barely write my name.