Actually in whole sign, as in every house format, cusps are very important! ONLY WE WHOLE SIGNERS CONSIDER THE CUSPS NOT AS BORDERS BUT ACCORDING TO THE ORIGINAL MEANING OF THE WORD "CUSP", IE "POINTS"-we call them "sensitive points" and they exist for each and every house in whole sign. WHERE are these "whole sign cusps"??
THE CUSP OF EACH WHOLE SIGN HOUSE IS A PROJECTION INTO THAT SIGN/HOUSE OF THE ASCENDING DEGREE OF THE RISING SIGN: so if say 18 Aries rises as the ascending degree of the first whole sign house, then 18 degrees of each subsequent sign IS THE CUSP OF THAT WHOLE SIGN HOUSE (the "sensitive degree" of each subsequent house)
So, in our example, with 18 Aries the ascendant, the cusp (sensitive point) of the 2nd whole sign house would be 18 Taurus, of the 3rd house 18 Gemini,....or the 7th house 18 Libra....etc etc, until the 12th whole sign house which would be 18 Pisces.
Planets and stars conjoining these whole sign house "cusps" are very important (planets aspecting. them are also important) for the affairs of that house (just as they are in Placidus or other quadrant house formats) For example, in the "Arthur Bremer" thread, in test charts A and B: the 12th house (house of limitation, self-undoing, etc) whole sign cusp is @ 2 Sagittarius, conjoined by the star Achrab (Graffias)-that star is rising and its indications for chart A 12th house are "...riches and preferment ATTENDED BY DANGER, violence, BENEFITS SELDOM LAST..."certainly applicable to the situation of the race car driver who died at 32 years of age in a car crash; in chart B, the whole sign 12th house "cusp" falls @ 22 Sagittarius, conjoined by the star Rasalhague, among the indications for this star being "...mental depravity...": although the term is old fashioned and intense, nonetheless one could apply it to the extreme mental retardation (12th house of restrictions and limitations) of the native of chart B.
So, yes we do have "cusps" in whole sign-they ARE important for us (we consider them to be generally more accurate than the house cusps of quadrant house format charts) and stars (and planets) connected with them, are potentially important delineative considerations for us...
Usually I would use Placidus. It is very sensitive to timing.
But this is not an asset if the birth time cannot be accurately pinned down. For example, if the birth certificate does not list a time, and Mom says her son was born "around 1:00" which could go 15 or 20 minutes either way (and possibly change the ascendant sign) Placidus can give a fake sense of planets' locations in houses.