Internal linear combination weights for SO LAT-like (orange) and FYST-like (green) experiments and SO LAT+FYST (blue) when the sky contains all extragalactic components (see Table 1), Galactic foregrounds, and atmospheric noise. Top figure: fractional contribution of each frequency channel to the recovered y-map. Bottom figure: frequency channels that contribute to maximising the tSZ signal and minimising the noise. The error bars show the standard deviation around the mean weight of all of the 192 tessellated fields for each frequency map.