I recently acquired a Surface Pro 4 (i7 6650U 2.2GHz 16GB RAM 512GB SSD Win
10 12.3" Tablet) and want to install Ubuntu 18.04 on it. I am following
this guide -
https://www.reddit.com/r/SurfaceLinux/comments/7kb1ky/guide_installing_linux_on_surfaceseries_devices/

Ubuntu will be my primary OS for this tablet, I hope!! Mostly
python/web/java/android development. Both CLI and the Ubuntu GUI.

First step - shrink the Windows partition and create a new partition for
Ubuntu. The SP4 currently has three partitions:

260 MB EFI System Partition
475.70 GB C:
880 MB Recovery Partition

Windows 10 needs a min of 20 GB according to the specs, but I have seen
recommendation to not shrink it below 50 GB. What is a minimum usable
amount?

What would you recommend for the size of the Windows C: partition and the
Ubuntu partition?

Thanks!

Mark