Well, I only went and did it😱. Bought the kit; drilled the hole; filed the screw; removed old, fitted new pistons/seals; bled system, and bingo; one rideable fatbike.
For one normally guilty of “fettling muppetry” of a high order, I’m pretty chuffed with myself today. Hopefully no, lever to the bars whilst slithering down a hillside, instigated death will happen first ride.
Thanks everyone for your tips and advice.