Peter.
Did you checked whether you can employ
socat instead of PTY's?
So, now you're running Debian-7.7?
Take a look at my site:
http://sp2l.ampr.org
to see what ham soft is running.
I have LinuxLite and Ubuntu-14.04 in VirtualBox
Had not too much time to play with, yet...
Best regards.
Tom - SP2L
(ex sp2lob)