Here is some technical talk from a reference that is seems to be widely accepted Parachute Recovery Systems Design Manual, T. W. Knacke, 1992.
PP 5-20
Figure 5-20 shows the possible increase in drag coefficient from line ratios, Le/Do, up to 2.0. Parachutes with no skirt restrictions, such as flat and conical circular parachutes, increase the drag coefficient up to the line ratios of 2.0.
Where
Le is the suspension line length
Do is the nominal diameter of the parachute (SQRT(4So/Pi))
So is the surface area of the parachute canopy including vents and slots
PP 5-21
Calculations indicate that line-length ratios above 1.5 may be detrimental because of the associated weight increase of the longer lines. Systems that employ parachutes in clusters or use first-stage drogue chutes require longer risers. Parts of these risers may be replaced by longer suspension lines on the individual parachutes to increase parachute drag and decrease the required parachute diameter and parachutes assembly weight.
I hope this helps.