i finally was able to try out the persistent port mapping per the link you supplied. I was not able to get that to work for me.
This is the example shown on the linked page I received from you. As I said it did not work for me. I do not know why.
# MoonLite Focuser
SUBSYSTEMS=="usb", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A501T0P9", MODE="0666", SYMLINK+="focuser"
This is an example I found on the Linux Mint forum. It did work as shown once I inserted the ids for my devices. The only difference I see is this part ENV{DEVTYPE}=="usb_device"
I do not know why the first one did not work, possibly something changed in Mint 18 that prevented it as numerous examples on the net are identical to your version.
Now for a clear night and I can try it all together. The only problem I still have is that I have to manually change the permissions of ttyusb0 and ttyusb1 each time I start up EKOS even though they both show the group as dialout.