new earth cable for Sterling Power unit

Well managed to run the earth cable through the bulk head hole behind battery! Bit of a faff because removing the battery would mean slave battery to keep the electronics going! But fortunately there was an accessory wire run direct from positive terminal. Which was run as a temporary live feed for led lights by the company who fitted the poptop and lighting! 

I had to remove the glovebox as expected but also the airbag panel on near side of dash ( on off switch). The lower plastic panel below glovebox as well, to find the the live feed wire.

I taped the earth wire to the live wire and gently pulled it through until I could feel the two wires ( the hole is just big enough under the dash to get both cables through but fiddly! As well as working by touch!!! .

Once pulled thru and panels etc replaced I thought I might as well attach the earth cable to the main battery. 

Good old VW .....not! 

The 8 mm nut holding the earth clamp onto battery post can't be removed completely only loosened the thread has a shoulder on it to stop this!!!

Which also means I can't add a 8 mm nut to it!

No where else to attach the new earth cable either so at this point I'm guessing a laborious filing of the top of the thread to remove the " shoulder" 

If I forcibly remove the nut It'll damage the thread and the nut. And not enough room to saw it off.

Option 2 is slave battery connected via jump leads to vehicle battery leads so I can disconnect earth clamp saw off bolt and fit new one!

Might be the easier option! Quicker at least!