Here's how I was able to output conky to a text file and then add it to my xfce4-panel using xfce4-genmon-plugin. Simply follow the steps below if you'd like to do the same.
PLEASE NOTE THAT YOUR CONKY MUST BE A SINGLE LINE OR IT WILL OUTPUT INCORRECTLY TO THE PANEL
1. Add the following to conky.conf....
out_to_x no
out_to_console yes
2. Set conky to output to a text file on startup....
I have the code below saved as conkypanel.sh & set in my xfce application autostart.
#!/bin/bash
conky -q -c /etc/conky/conky.conf > /tmp/conky.txt
3. Add xfce4-genmon-plugin (Generic Monitor) to your panel and then add the following command....
awk 'END{print}' /tmp/conky.txt
4. Conky should now be displaying inside xfce4-panel. If not then start from the top and double check everything including you conky.conf....