Photoscene...
"I have a total of thirteen must have items on my desktop. I can add one more before they start stacking up. Using an icon size of 72 the screen will hold 36 items."
Depending if there is a file name overlap/resolution settings, a 72px icon is over 1" square on my screen. (about 3/4" for the icon + 1/4" for each line of text, up to 2) Then factor in the icon spacings. I would be pulling my hair out as only 12 will fit on my screen at that setting, even though I am not a fond user of DT aliases.
Maybe it is me, but I think it is a bit too much to ask for the DT to hold that many items without having the fits you describe at that 72px setting. I keep mine set around 36-42px depending on my mood.
Please note, nothing personal, but if it doesn't work right, adjust...
Other than my 30 items in the Dock, I also use
HimmelBar, a neat 3rd party application.
...Ron