serifs in u.sc.ss01 vs u.sc

[schriftgestalt]

Is there a reason the serifs in u.sc.ss01 are much smaller than in u.sc and h.sc?

It affects the metrics key (the RSB is linked to h.sc) and that results in tighter spacing. So either use the same serifs or use a metrics key like this: "=h.sc@300" (will use a measurement line at y=300 to calculate the spacing).