I made mine bigger than stock and it worked great! One thing I don't get about the rudder deflection method is that I always felt like the rudders were not very effective, and I guess in my mind I justified that by the high angle of attack on landing that the fuse was cancelling out the rudders?? So if that was true, I'm not sure how effective deploying the rudders would be, plus between the two, they do not even compare at all in size to the stock speed brake.

I wonder if it's possible that the ones that flew that way had an exceptionally placed CG and since delta wings slow down so well anyway, that it was just observed that they slowed down well using deployed rudders and maybe it was just all that fuse and wing at a high angle of attack that was doing it??

Don't know, but the reality is that the roo might not even need a speed brake if you get the CG right??