I've already tried using my air impact wrench set at about 110 lbs (just about the wrench's maximum). All that did was bruise the nut.
I've got a quality clutch holding tool braced under the slider. Then with a long socket wrench pointed upwards I'm pulling while anchoring myself with the rear subframe.
OK thanks all. I'll give it another go this evening. If something goes snap, oh well. It's taking a lot more force than the rear wheel nut (which I've taken care of on regular occasion) which I thought is funky so I had to post my above question.
my nut was very tight 1st attempt fu*ed the basket so new one needed, but with a helping hand and the proper tool all be it made up myself, my nuts come off now na probs!