DCM matrix / model steering

Hello
I got correctly working DCM matrix using gyro's data, but I need to complement this matrix with steering input for RC model. What is the best way?
I achieved this with mixing sensor data + steering data in update matrix for DCM and it is working quite good. But I think it is not correct way, since I loosing original information about model position and I am not sure about precision.
I dont know how to do it separately, e.g. DCM matrix * steering matrix. When I tried it, it not worked as I need (for example, after turning one axis to 90 degress, other axes were rotated in some weird way when model was turned to 90 degress too - compared to previous solution of mixing DCM with steering)
I am not so confident in this area, so I would be glad for any help

Thank you very much