tack:
As far as the LCD spin out goes, I only put that there as I've not used a 20x4 display so wasn't 100% sure they were all identical. I'd guessed they were as the backpacks work on those two, but safer to have the OP make sure.Hopefully he'll report back if it's worked for him. I know some people can get tremely frustrated when things don't work and get the 'it's no good, I'm fed up, it's rubbish' red mist. I have a couple of mates with low patience levels like that.
OMG (as the kids would say)!
I wanted to do things by the book (i have seen many posts about non-soldered LCDs, wink wink), so I ran the I2C scanner.
x20, and not x27!
I wire it up using my old floppy cable, and the frickin' backlight comes on!
I download the new I2C files and copy it to my library, copy tack's code, and 
tack wanted to make sure I knew how to fix code......ahahahahaha. A few ; here and there and it was ready to upload.
Mama Pajama! I could see some stirring in the LCD, so I gave the pot a few twists, and MONEY! We have a working mjkdz LCD I2C backpack!
I am now troubleshooting the fact that my "R" in "FORUM" looks like this:
instead of this:
I will mark it solved, since I can see clearly now the LCD.
Again, many thanks to all of your for your tips, expertise, and encouragement.