Well, I'll give you the same usual advice......... call Cape Cod Shipbuilding.
However, I know that they use a special adhesive on their other boats, so perhaps they do the same on the DS IV. I looked on their website but it only lists the price for the rubrail (on the DS Parts List), and the Rub Rail "kit" (I assume that includes screws or glue).
Best advice is to give them a call, or maybe post this question on the DSA web forum,
www.daysailer.org
I know that I looked at an older (1973-5?) DS II at D&R that had an added rubrail and it had been attached with sheet-metal screws as best I could tell, although the screws were short enough to just barely stick through the underside of the hull-deck joint. For any non-DS II owners, the hull-deck joint on the DS II is sort-of an outward turned flange that curves over like a plastic bucket rim, the deck edge is bonded over that like the lid of a trash can. See drawing below, I am reasonably sure the CCSB Day Sailers are similar, although the joint is squared off, not rounded.