P50 Xeon 4k and woefully uncontrollable vbox guest scaling

Evening everyone, loving life with Ubuntu mate 20.04 on my P50, very smooth UNTIL I decided to fire up a few virtual machines in VBox. With a 4k screen, the guest comes up microscopically small and I have not found a good method to increase the scale without dastardly side effects to the main desktop. Any kind advice would be appreciated. On a side note, when connecting a 1080p second monitor, the interaction between resolution hunting and the main screen makes both go bananas unpredictably. Fonts, window sizes, you name it, crazy. Unplugging the second monitor and we stabilize, but frequently will not restore to intended settings for the main monitor until a reboot happens.

Bob
Lenovo P50 Xeon
4k display
Nvidia quadro discreet graphics