Please help review my DCS TIU track plan (attached)

I am using 2 MTH Z-4000s and one TIU for a 3 level track plan.  Does this look like the best way to hook up the wires for running both PS2/3 command and conventional trains?  Since the first level would be most often used for command, I thought the fixed outputs would be best to use there.  And then I thought it best to hook up my 2nd Z4000 to the variable outputs for levels 2 and 3.  I would like to run command on all tracks or conventional on some and command on others.  I don't need to run command and conventional at the same time on the same tracks.  I do have an extra TIU -- should I use that for the 2nd Z4000 instead of cramming everything into 1 TIU?  I have all of the books and videos on DCS including Barry's.  Your thoughts, fellas?  Thanks, Mike