Retired plumbing is correct with the codes.
no more than ONE slipjoint after the trap..In fact it is common code in most of the CIVILIZED world!
Retired plumbing has forgotten more about plumbing then you will probably ever learn JOMEISTER! I dont know what your beef is with him but you should be learning from him not badgering!
(to get technical, there is supposed to be a de-sanko fitting on the sanitary tee if using a tube trap)
This board blows!