Spring Plate Torque

[BSNMOE]

I'm having difficulty torquing the spring plate holding nut to 180 FT lbs. After bending the very thin suspension wrench I ground down my own.
The problem is with the angle I need to use a universal attached to a long extension to clear my 930 fender. It's hard to hold that steady and even though I'm using impact hardware it flexes quite allot. I'm worry it could slip and even with a friend holding the thin bolt head it just doesn't seem safe.
I'm thinking of heating the nut to expand and then hopefully it will torque easier or maybe use a 1/2 in drive battery impact wrench to spin the nut fast without holding the nut. Also I believe this impact will fit inside the fender.
Any thoughts on this?
Thanks