Top panel: the blue curve shows the difference between 143hm1 × 143hm2 cross-spectra between the 2015 (destriped at N_side  =  512) and 2018 (destriped at N_side  =  2048) data. The red curve shows the difference between the 2015 solution destripped at N_side  =  512 and at N_side  =  2048. The green curve shows the improvement brought to the 2015 data by the use of the better 2018 gain solution keeping the destriping at N_side  =  512. Bottom panel: associated level of improvement of the variance ratio between the destriped 2015 data at N_side  =  512 and N_side  =  2048.