I always thought from Ad Konings' books and the photos I've seen of elegans that they looked more like M.livingstonii!? According to the link above, M.elegans can be told apart by the extended anal fin from M.livingstonii and other than that they look very similar.
Personally I don't think "acei" should be in the Pseudotropheus group, they just are too different IMO. Body shape, feeding behaviour, aggression levels, etc. The fact that they are non-territorial should be factored in as well, considering many of the Pseudotropheus group are highly territorial. I think Gephyrochromis would be a more suitable genus, but I don't know the details on how "acei" differ from G.lawsi and G.moorii.