You need to let us know which welding process is being used before we can comment intelligently. You may look the essential variables up yourself in QW-25X. Since you used the term 'electrode' in your post I am making an assumption you are talking about SMAW and, if so, a change of groove design would be considered 'non-essential' as it is with nearly all of the processes. This means you may modify the joint details without requalifying the WPS but you should revise the WPS to allow the change. Maybe to avoid future concerns in this area you could simply include a statement which address most 'typical' joint designs. By the way, just as a clarification; you state the PQR is qualified for 60mm, depending on which Code governs your work, ordinarily your WPS would be qualified for 2T in accordance with QW-450 but I would definately double check the constructing code before making that assumption!