I'm sure the 1847 Medusa is still less than 20 Richard, and likely to remain so. There was only one of those on ebay in the 5 year period. It was around £15 until the last few seconds, I was amazed when I bid £500 about 3 seconds from the end and was outbid. It was the chap who used to buy on ebay with ID bargains1*, now sadly passed away, with his coins sold off very poorly and cheaply.
Re. the Large Rose again, I would be intrigued to see how long it will take you to get to 20. If you were to regard as two separate types then I really think you would struggle to get to 20 examples. My guess is that you may not even get there with the Small Numerals type with the flaw through the 5. I could keep my 13 pictures to one side, or share with you first if you wish, and then they could be cross checked to any new ones reported.
Depending upon sub-level, within each year in this series, there may be other candidates. Off top of my head, 1854/3 (real ones!), Bramah 3b, the 1843 DFF, 1853PT with the italic 5 date style, a couple of 1845 date varieties (not the obverse with the big die flaw at front of truncation).........and then there are always the dots, ha ha!!
Just a thought