I built such a system for my former AS-W12 using a Cleveland system.
Worked fine but make sure the entire system is as stiff as you can
possibly make it. Use heavy motorcycle bowden cable and make the run
as short as possible. Also make sure the master cylinder mount is
rigid.

The ratios from brake handle throw (e.g., what is the max throw you
can get with your hand on the stick) to the throw on the master
cylinder actuator is an interesting geometric cut-an-fit. Making your
own handle will help a lot.

I much prefer spoiler-actuated brakes due to the additional force you
can apply with your entire arm/shoulder, the fact that both drag
devices are appropriately on one handle and the difficulty in mixing
fine-scale pitch/roll inputs on the stick with the gross-scale motor
skills of pulling like hell on the wheel brake.