To easily convert metric torque to standard....go to http://nmbtc.com/Calculators/converter.swf

Click Torque tab and click on Kg/cm in choose units row, enter Kg in "convert from" window. Click "calculate". Read oz/in.

Very accurate. I get 55.5 oz. required....not a lot of torque but according to the manufacturer, the 75 oz. of your 3421 should be adequate. I think they're using small servos to minimize tail weight. You decide whether overkill on the stab servos warrants lead in the nose,

W.

FWIW Alan, the JR DS9301 is the Japanese version of the western JR DS3421. They are identical servos.