Kiwamu, Stefan Tonight we copied the BS OPLEV filters to the BS M2 LOCK pitch and yaw filters, and modified them slightly to get some moderate DC gain on top of a significant suppression at the optics resonances. - The modification we made is PIT and YAW: FM1: zpk([0],[100],1,"n") was replaced with zpk([0.1;0.1],[4000;100],0.2,"n") . Together with the WFS filter bank (a simple 1/f integrator) this results in very weak DC feed-back. PIT: We added a 1.2Hz resonance peak compensation and a p0.1:z1.5 low frequency boost to FM10: zpk([0.02+i*1.2;0.02-i*1.2],[0.200028+i*1.18338;0.200028-i*1.18338],1,"n")* zpk([1.5],[0.1],15,"n") The results in a reasonable secondary UGF crossing. Pitch was tested, and resulted in a unconditionally stable loop. Yaw wasn't tested yet. A snapshot of the engaged filters is attached.