So a 4' tank, I'd still do fish where the males stay around 10". Anything larger and they just won't have the space needed. JD,gt,cons,fm,salvini, are all good choices and really not any harder to breed then the other once paired up.
The larger species rd,Midas,festae,RTM,jags,trimac's for example all are best kept in 6' tanks to a breeding pair. Gives the males more room to move about, with their hyper aggression and usually larger size, they often will not take any nonsense from the females.
Best thing you could do regardless of the species you pick, is have a divider on hand and ready to be used. Because if he's ready to rock out... And she's not... Chances are he will kill her.