Wim, the problem is your Mac I think.

What I do is to restrict myself not to the limit exactly that Renderosity wants but to 12K. Then there is enough scope to balance out the differences between Mac file size calculation and the Windows method.

Reason for that is the difference is the way disks are formatted - into little minimum sort ot atoms. And those are different in size on Mac and Windows. And therefore the file sizes can differ.

What I do therefore is to save my files for posting always through "save for web" in Photoshop. The original file I normally limit there to 195K, a limit for a lot of sites I post and the thumb then to 12K (200 pixel on the bigger side).

This works.

One day your ship comes in - but you're at the airport.