This is a fix post:

I was running Kubuntu 18.04 beta upgrade over 16.04 LTS and was happy with the results. So being the clean and tidy person I am, I did a clean install of Kubuntu 18.04 now that it's released (Home is backed up regularly on another drive). Everything went as expected except that my Uptime Monitor by Clearmartin would not resize vertically. Very odd as several other widgets I installed work fine, and I really liked having an uptime on my second monitor...wasn't happy. But I figured it to be a config issue of some sort since Clearmartin hasn't updated the widget in a long time, and adjusted the widget size manually in the config file, rebooted, and it now sizes properly.

So for those having any resizing issues, enable hidden files if using Dolphin, from Home folder open to the .config folder and edit the plasma-org.kde.plasma.desktop-appletsrc file, find the applet number that corresponds with the widget and you can adjust the size. Parameters of the Containments section are simple:

[Containments][2][General]
ItemsGeometries=Applet-26:640,768,256,96,0;

Applet number (first number) can be found in the file, just look for the widget name and you'll get the applet number. The next 4 numbers refer to pixel location from lower left of the screen, so 640 up and 768 in, 256 pixels long, 96 pixels high. Not sure about the last number as they're all zero.

My issue was that no matter how I tried to resize on the screen, it wouldn't go above 48 for the height. Manually changing the height to 96 saving and rebooting immediately would start the session with it sized correctly. Lock the widgets and it will retain it. You can edit in Kate and you don't need SU privileges.

Hope this helps.