Based on what the breeder says that I got part of the black line from they have zero Sumatra in them. I do agree though that the head seems to resemble Sumatra a bit. He is 5 1/2 months old.
The lobster tail is almost impossible to get if you don't already have it. It's even difficult to keep if you don't continually keep after it.
Sumatra tails are not like Cubalaya tails, from the side it kinda looks like it, but in formation they are not alike at all. The Sumatra tail is vertically wide, the Cubalaya tail is horizontally wide. The Malays do have the shrimp tails and could be a good breed to use, but it'll take a minimum of 5-7 years to get a good lobster tail unless you are willing to hatch 100+ a year and select from those. It is nearly impossible to do it quicker with low hatch rates but you might get it done by chance. After the first generation you can no longer use the Sumatra as that would be going in the wrong direction of a horizontally wide tail.
You are right. Sumatra are also different enough structurally that it makes it difficult to get back to the Cubalaya body structure. It takes lot of hatching and selecting to get the Cubalaya traits.
.
.
