So, I have been waiting for time to take a good look at the Wright & Page revision on this one.
I think there is no reason to disagree with this being a maturing
some Tanganyikan synos have this high back and the predorsal profile was odd to me but I think just because we are used to looking for this in hybrids. As has been pointed out this fish matches nicely with the Lectotype in the revision and the fact that the smaller of the two purchased still has the bars on the caudal helps as well.
It would be nice to see more proof of these and now we know what to look for that may help.
I have seen other hybrid mixes of tanganyikan synos but I do not believe this is one.
Birger