Per my Google Fu, I know this is at least possible. My question to all of you, is how do I do this? There is no such option in the system tray config itself. I need to get it up to at least 64, maybe 48.

Release Notes For 3.5.11 - Trinity Desktop Project Wiki

Apr 21, 2014 - 1 New or Improved from KDE 3.5.10. 1.1 Back ... The System Tray icon size is now configurable, per the applicable Free Desktop specification.