Hi Nique! The only way I know how to do this is to have panda running full screen. You can do this with the following python code at the very very beginning of your program.
from pandac.PandaModules import loadPrcFileData
loadPrcFileData("", "fullscreen 1")
However, I personally hate splash screens because they always seem to cover up what I am working on. Yet it remains a popular convention, such is life.
You can use WindowProperties.setFixedSize to set a fixed size for your window, and the “undecorated” option / config var to entirely remove the window bar.