Bike porn

Please correct me if I'm wrong, but in the 90s Hope made a twin front disc setup with Pace. Swear I remember seeing pics of it in the bike mags of the time for DH racing. It ran from one pretty normal looking sport lever to two twin piston calipers (XC2 calipers?).

Really if you do your maths/ get your micro-calipers out, you don't need two masters at all. Just one lever, but a larger volume job, say that of the monster Mono6 caliper from a few years ago, and then two mono-mini/mono-moto calipers use that hydro 360 headset thing, then make something so you can attach the two frame side hoses fit to the one out let from the hydro headset. Balancing might be interesting, but TBH there will probably be something ideal in the RS catalogue (almost always is) for flow/pressure reduction, or even a decently controlled bleed session would be fine for the most part.
with that ^^^^ you might be lucky and be able to do it with all off the shelf parts for not a lot of money (£120? with used calipers/lever, new headset thing, and clarks braided hoses).

Talking of trashing hoses, I've been riding hydro discs on all my MTB's for 12yrs+ and I've NEVER bust a hose (and I used to crash plenty), I only use what they come with (mostly Hopes, had one set of hayes and two sets of shimanos, shimano had the poorest quality hose/hydro fittings by far).

It wasn't Hope, It was a company called "The" who made and advertised dual front disk brakes in all the relevant 90s Magazines. From memory they went bust as they were overpriced and underpowered when compared to their rivals (This is not that same as "THE" who make mountain bike and motorcycle protective gear.

Avid BB7 brakes are amazingly powerful when set up properly and to for polo really really make sense. As someone who played in high level competition and broke enough brake set ups to appreciate the ease of quickly fixing a bike court side to get back into a game usually with the wrong bits for the job, I'd recommend you listed to Rik as fixing a cable is far easier than fixing a hose and I've definitely had incidents whilst playing which would have left me riding a borrowed bike rather than fixing my own and getting back on court on the bike that I was used to.

That said, I'm a bit of a geek and did look into building a dual hydro set up, more out of curiosity than anything else. I discounted using motor bike levers as they're too damned heavy and the lever blades tend to be far longer than I'd like.

This looked interesting but never made it past the design phase as far as I'm aware.
The lever works on two planes so pulling it like a normal lever operates one brake and pushing the lever down (90 degrees relative to the normal action of a brake lever) works the other separate Master cylinder. My concern with something like this would be using is efficiently whilst throwing the bike the bike around during a polo game. Theory say's it should work but I think that in practise it would be a little awkward.

Although I never wrote off the idea as unworkable, I did stop playing polo and naturally stopped thinking about ways to make this work. That said, I still believe that it's feasible and provided you do enough research into Master vs slave piston diameters, take into account the volume of fluid you wish to move and accept that you're probably going to have to set the pads closer to the disk than ideal (meaning brake drag when you bend your rotors) and work out a sensible hose routing with good braided cables and you're onto a workable system which should be durable though it's the times it does go wrong that you need to really worry about.

If you travel a lot for polo I'd stick to cables, if you just want to do it for fun then start researching hydraulic brakes in general and in particular I'd personally pay attention to trials riders set ups as they really know about brakes. I'd advise thinking about what makes a brake good for polo versus other cycling disciplines standard requirements, you want the brakes to bite well but could sacrifice some hold, would you wish both brakes to bite equally, is hold more important in the rear or the front or not an issue at all.

I'm going to shut up now.