I have had this hybrid occur. It is definitely possible. Though unfortunately I ended up getting the fish themselves, not knowing what their bloodline was. The resulting offspring have a tendency to have females turn yellow as the Lombardoi males do. Also, almost all the fish get the higher number of stripes on their side. According to the articles of Ad Konings, the Lombardoi ought to have 4 stripes in the region below the roots of the dorsal fin. Where salousi have 6-7. I've been breeding the mixed blood out best I can, but it's maybe 5/100 offspring that gave me the 4 stripes. Still, females sometimes turn yellow. It would take several generations to get them right again. The same problem occurs with Pseudotropheus Demasoni, which also ought to have the 4 stripes on the region below dorsal roots. All mbuna are genetically viable. And genetic flow between species is common even in wild populations. However it's limited in that case by geography. They only mix from time to time with populations that are closely located. This makes accurate descriptions harder for individual species. Though I prefer to defer to the descriptions of Ad Konings. Most reliable source.