Hi John,
So was the hand brake cable touching the chassis seat rail all the time or just when the shock was loaded?
I had a similar problem with mine when I fitted the cable. I ended up fitting a angle bkt to pull the cable away from the chassis seat rail.
The cable cleared just
when I removed the shock spring and moved the damper through it's full range.
I know it looks close to the drive shaft and suspension arm but it clears these as well.