Almost  identical  situation  'here'.

16 foot  Macdon,    and  16 wheel    Rowse.

When I get into  the  light stuff,   It's  going to be bar mowed anyway,  and  I'll dump rake  a  nice sized  'row,     sometimes  that  can be  100 foot apart!   Imagine   wheel raking  all day  for  a near invisible   windrow!

Anyway,     raking  3  rows   and  using a  kicker for the  middle  is  still going to  put the  whole  combined  right back on the  wet ground of the  original   middle.   You are correct,    without   splitting the  center row  equally,  you'll  get  a  lop sided  'row.

what  I do,  on the rare occasions  where     2  combined is  still too light,  is  combine 4.    

Crowd   row  1 and 2  towards    row  3.  

Come back and  crowd    3 and  4  towards    the already  combined   row  1 and 2.

THEN...   pull the  whole  show  into 1.         Beware,   you better not get too far in front of the baler  with the final  pull!    Break downs,  rain (which hasn't been a problem this  summer!)  and  wind   will   screw you.

I think  the   'Ultimate  rowse'   will do  all of  this  in  one pass...    All it's  takes  is  a   crate of  cash,  and  a  200 horse  tractor to pull it!!