High Voltage PCB Design
20 mils separation between the 80V and other low voltage signals or the GND is not enough clearance. I have just recently done some PCB design work that has an 84V power rail. I've had to ensure that the clearances between any 84V net and other signals is over 47mils and preferably even more. I can refer to some supporting information on this amount of clearance but do not have access to this information right at the moment. (I'll come back and update tomorrow). 

In my case I also took the course of action to put all the 84V layer and trace connections on an inside layer. The reasoning for doing this was because solder mask is fairly thin and can be easily scratched and expose high voltage on outside layers to potential shorts. I also had to worry a bit more about this because the 84V rail in this design has to support AMPS as opposed to uA. 

Edit

Here is the info I promised regarding PCB clearance guidelines. In that page is a slick little calculator that helps with recommended trace clearances.