Oh well. It took more than two years, and I got to change my email address in the process, but now I have revived the game, added an option to have up to nine save files on a floppy. I'll mail a link to Stadium 64 soonish.
I noticed the screenshots for the re-release Soccer Boss on this site are different than the ones on e.g. Lemon 64. I thought the re-release was the exact same game, but it seems to have been visually improved a bit so while the game engine probably still is the same, it looks a little different. The screenshots of the ZX Spectrum and Amstrad CPC versions suggest this as well, although I don't know if the "original" Peaksoft version was available on these computers.