Vmca
Yes, I thought that might be the case and I'm glad you've confirmed it.
Thanks
FAR 23 (light twins) and 25 (medium) actually defines Vmca is at weights that most adversely affect directional control i.e. highest speed, not necessarily at max weight. However, all of the aeroplanes I'm familiar with state that Vmca is at max certified take-off weight.
It's interesting to note that, as one reader pointed out, at least one aeroplane (Caravelle) does not have a Vmca as such.