"Yes, I think these are Phyllidia carlsonhoffi. This is a difficult group. These "Phyllidia varicosa look-alikes" are often variable and there is frequently no good line of demarcation between what we currently consider different species. I'm sure there are identification errors on some of these species on all the web sites, including mine. Dorsally, these look like what I call Phyllidia carlsonhoffi here in the Marshalls.
However, I have seen Phyllidia madangensis that could not be distinguised dorsally from Phyllidia carlsonhoffi. You'd have to look at the bottom of the foot to be sure -- Phyllidia carlsonhoffi has a dark line running down the center of the foot bottom, while Phyllidia madangensis has no such line."