yes, you are working too hard!
Secondly, icons can be up to at least 256 square now... There is a little bit of prep work, but this is 2 step process. A. Create a Render Setting to create icons. Include the size you want. (You'll probably have to set this every time, and you'll need to reposition the item into the render area.) B. Control G to turn off the ground plane. Gives you a clean white background.
C. Save the new item to the library
Make the icons.
1 Render the item with your pre-made Render settings.

2. Save to the folder it lives in from Poser, overwriting the icon Poser generated for you.

;>

Andy!