Building an [Ubuntu 14.4 LTS](https://groups.google.com/forum/#!topic/qubes-users/w0uZNr8nno8) template can be difficult.
A workaround is creating an ubuntu HVM A and use X over ssh from a second vm B ([see](https://groups.google.com/forum/#!topic/qubes-users/-wkG7E55PUI)).
To do this you have to enable networking between A and B, or set B as netvm of A.
If B supports copy and paste or seamless mode so does (indirectly) A. (you will be missing some features. e.g.: send file to vm A)
Doing this reduces the security of A to the security of B!
This is no problem if B's only purpose is providing X over ssh only for vm A.