David Allingham continued his strong start to the penultimate round of the championship as he stayed on top at the end of FP2.
The championship leader went quicker than in the first session, clocking a 1min 29.464sec lap to end day one ahead, 0.310secs clear of Ash Beech.
Luke Mossey, who trails Allingham by 42 points in the title chase, was third with Ash Barnes fourth and Declan Connell fifth.
Pirelli National Superstock Championship, combined practice:
1. David Allingham (SMS/Nicholl Oils BMW) 1min 29.464s
2. Ash Beech (Jones Dorling Racing) +0.310s
3. Luke Mossey (Milenco by Padgetts Motorcycles) +0.381s
4. Ash Barnes (Rapid Honda with Drivelife) +0.432s
5. Declan Connell (Rapid Honda with Drivelife) +0.851s