Yes and No. All of those are too much for the tank, but He could very easily keep both JD's in that tank with no problems. Right now I have a 9" synspilum and a 7" dominant male JD in my 55. I only remove the JD to one of my other tanks when I am breeding him. Otherwise they live nicely together.
o snap its eric: That 1 gallon per inch rule certainly does not apply to larger more aggressive fish like cichlids. Barbs and such ...ok sometimes but not always.
But it certainly goes out the window with cichlids. You can't say that in 125 gallon for example stocking sixty-two 2" barbs would be the same as twelve 10" cichlids in a tank.
That is the beauty of cichlids. Most of the "rules " go right out the window. You never know what kind of fish you will get. I have tried combos of cichlids over the years that others have been successful with and failed miserably. On the other hand I have combos in my tanks right now that some say I shouldn't have and will never work. But they have and are. Have been for the 20 odd years I have been doing this. That's cichlids. That is what nmakes them so attractive to the aquarist.
My 2 cents.