Samson, I would recommend to resize the image on your PC at EXACTLY 800 pixels to avoid the automatic resizing at, in this case, 799 pixels. I am sure this one is worth the little effort. How to do it:
* Resize the original image to 800 pixel and do the last finishing.
* Clic on My Gallery and clic on the current image
* Clic on Edit Photo at the right side
* In the Gallery Image Editor select the new image that will replace the old and submit the changes.
* This way the image is changed but you keep the rest...
Hope it helps