Hi there guys, I know this thread is about 3 years old but I need a bit of advice - I have tried everything in my power to get to the nut your talking about on the arm - I know normally you can slip a 17 spanner in securing the top nut while using a ratchet to undo the bolt but unfortunately for me the nut has gone a bit soft so neither size spanner will grip it - I have tried with mole grips but because the space is so tight they keep slipping. I have thought about cutting the bolt head but again as there is no room I would be unable to slip it out - any suggestions?