15/16 is the bm44 master it will be fine. i m running a bm 50 (1 inch) master on r32 calliper all round but haven't tried it yet so cant say anyting on how it feels but as i read from previous post it will be fine.

Sorry mate I gave you a bum steer. My MC is actually 13/16". I have edited my initial response.
Pedal is very firm with minimal travel.
A Silvia MC and booster will not fit in a 1200 with a CA. I've looked at this myself.

The S12/13/14/15 booster & master are about 230mm wide & 250mm from the firewall to end of the master. I'm using an S15 master on my S12 booster with a bias adjuster. Because it's meant for ABS & 4 pot front calipers I had far too much rear bias using SR20 front brakes and 910BB TRX rear discs. Now that I have R33 4 pot fronts it's back to needing front bias.

i'm just using original master cylinder (11/16) adapted to disc/drum

I really just want something easy - pretty much bolt up. (does it?)
Is the S13 booster large? I will be squeezing it in beside the CA18 manifold.
How does the pedal feel matty?

Hi mate
I'm running SR20DET front and R31 rear brakes with a 13/16" master cylinder and no booster.
I love it as is but if you wanted boosted brakes why not use the master cylinder and booster assembly from an S13 Silvia.
Matty

I was just wondering what sort of Booster / master combo people with S13 brakes are running? (and what size)
Do you think 15/16 would be too big?