Oh, a pirate dish! I see now. :up
You could have gotten all sorts of confusing advice if you hadn't posted that picture.
I wouldn't worry about using anything but a stock round-feed LNBF on it, it's not really an elliptical dish, for the purpose of discussion.
(and more conveniently, the less-common rectangular-base type, as you currently have)
As long as it's big enough to discriminate against the adjacent satellites at Ku, you're good to go.
Curious what the height and width are, though.
And if you should get froggy and want to use other of the more common design LNBFs, we can point you to LNB brackets that you can bolt on to hold one.
Likewise, I won't jump up and down to encourage you to bolt on extra LNBFs beside the center one.
Might have useful spacing, might not. Most likely it'll be 9°, if you want to think about it.
For now, if you have the desired bird, no reason to complicate the discussion.
Congratulations on getting your signal.