How does ranking adjustment in Wii Sports Boxing work

Unfortunately, I don't think there is a stamp overview page. However, as a low-tech solution you could note on paper which stamps you have completed, like this:

Air Sports: (x) (x) (x) ( ) ( )

Archery: (x) ( ) ( ) (x) ( )

This is difficult, but it's not impossible. You've passed the first hurdle by recovering the RPSports.dat file, the next step is popping the file into a hex editor and looking for offsets.

Start with a blank save file and save the minimum amount of detail - record every bit of that detail in a log. Open that file in a hex editor and look for something that makes sense- I would search for the date code stored in bitfield format. From there, you can begin searching for offsets and values stored in 2 bit hex strings.

This is a great intro to the parsing subject: jansenprice.com/blog?id=9-Extracting-Data-from-Wii-Fit-Plus-Savegame-Files

I was able to use many of these details, and a lot of tinkering to create an online parser for wii fit weight. I started with a parser that I found, and just converted everything to plaintext hex with binascii.b2a_hex (python) so i could figure out the correct values and worked backwards until it worked. You can see my working parser at http://www.getmyfitdata.com - it pulls weight, date, balance, and bmi from the wii fit save file.

Can you post some details about the RPSports.dat file so we can begin looking for values/offsets? Specifically, what date was it created, what was the score, what was the Mii name, etc.

It looks like game data starts at offset 0x2CC with 455 bytes for each game store.