This is exactly I done with my first roo, It had no speedbrake and landed quite well, but I lost
it in a unintentional inverted flat spin that I went entering a looping. be careful if you put the cg
aft... on the second roo I installed the conventional speed brake and the plane was a lot easier
to land and it uses a single servo (also used a cheap giant servo). The rudder deflection method works, but I still prefer the standard speed brake system, mostly because I like to have
as many resources as possible to control the plane at low speeds in the final approach. If you
are using the rudders as speed brakes they loose almost all of their action. Hope this helps,

Enrique