I'm having the exact same problem:
http://unix.stackexchange.com/questions/233163/how-to-fix-x2go-desktop-that-does-not-resize-contents-to-fit-in-remote-desktop-w

Except that I erased the .kde config, to start fresh and it did not improve the situation. I also specified 800 x 600 as window size, but x2go resizes the window without me asking to do so to full display size and it is still not enough to display everything, the task bar for example (kde) is off screen.

Thanks

Markus
--
Por sperto kaj lerno ne sufiĉas eterno.