This is what I think SP-D fuzzyball arrangement looks like. I wonder if there is the possibility that there is N terminus binding more similar to SP-A and MBP, the lateral associations (as well as a hairpin turn between two trimers of SP-D to form a fuzzyball with a “hollow” (more or less) center as seen in many images.  Two images here from a 14 armed-fuzzyball of SP-D (image not mine originally but highly processed for showing the N termini, the collagen-like peaks that occur along the arms and the possible neck and then the prominent CRD domains.  It is a thought…. you are free to criticize and discuss… but this is a visual assessment only, i have no data except three years of “looking” as confirmation.