So I get the error -1 as well. As far as I'm aware I've done all the steps correctly but I'll still give a detailed critique of what I did and maybe you can find the kink.
First off I downloaded both of the files needed.
Secondly I created a "root" folder in /external-sd using root explorer because I did not have one previously.
I then moved the BGH file into /external-sd/root
Next I changed the ID to be my android ID and saved it.
I then exited root explorer and launched z5, it failed.
I went back into the root folder and found that the ID I put was gone. Literally just gone.
I changed it to a random number, saved, exited, came back in and it had also disappeared.
Any ideas as to why this is happening?
Yes, I know what's happening. You aren't supposed to make a folder called "root", root of your sdcard means no folders. Like if my sdcard is "J:\" then I would paste the BHG file on that directory, not in "J:\root\"
Edit: And are you using your phones built in 'external' storage? Because that could be causing problems. I don't know if this app just looks for the file in /mnt/sdcard or /sdcard, that's probably what it does.
Also, you might have not pressed save when editing the BHG file with root explorer, I have done that a couple times.