There doesnt seem to be a lot of ppl still modding SH3 these days, that might explain the lack of answers.
Here is the link to the UI with the chronograph. I cant tell you exactly what i changed, because its been quite a while since i made that mod. And my memory isnt what it used to be haha. But take a look, do a file compare with the original file and you should see what i added. WinMerge is a good free app for this.
Also, Please remember that its not just a matter of modifying the menu file, you also need to add several other files like images, etc. They should all be included in the mod i linked to.
http://www.mediafire.com/file/7azlci...EN-V2.zip/file
Hope this helps.