One embodiment is directed to a method for creating translumenal vascular access, comprising utilizing a dilator adaptor to assist with forming a substantially atraumatic geometric outer junction between a dilator member/introducer member assembly and a guidewire which may be somewhat undersized relative to a lumen formed through the dilator member, thereby creating a geometric fit gap which may be suboptimal from a tissue interfacing perspective. The dilator adaptor may be interposed between the guidewire and dilator member to assist in remedying this fit mismatch, and in generally providing a preferred outer instrument interface for insertion through a small defect in a vessel to gain access to a lumen defined through the vessel.