What do you send to the OSC input of MadRouter ? Integers ? Floating point ? What value range ? If you send a float between 0-1 and you forward it to DMX output channel, it will do a round(floatValue * 255) so it should be ok.
Also if you monitor the OSC input device channels (double clicking the input device in the device list dialog), can you see your channels changing ?
Matt - MM tea