You and Chartman were spot on with the instructions on adding charts to posts. The reason it wasn't working was for some reason I had the option to show images turned off in this particular forum - an oversight on my part. So now you will see your charts are showing correctly. The only problem as I'm sure you can see is the charts are soo big they mean you have to scroll the page right to see all of it. If it's possible you might want to descrease the size of the chart or shrink the image, though this often leads to an illegible chart.
Soon, we'll be upgrading the Bulletin Board, and this will allow you to not only display images but attach files - which may prove a more successful alternative to displaying large images within a thread. Though I do find it convenient to see the chart as I read member's posts.