Magura 13 on a single piston

[Clutchup]

I tried setting up my handbrake on a 4 piston and I think the bracket moves a little but I ran it to my stock f2 rear caliper and works kinda but weak. How are these masters on a single piston? I can't seem to bleed this master at all I don't know why I get a good feel pretty stiff just not strong.