Sorry, i’m a bit rushed for time so I can’t answer properly, but a simple way is to go via a TriMesh.
TriMesh mesh { TriMesh::Format().positions() };
mesh.append /* blah */
auto vbo = gl::VboMesh::create ( triMesh );
Something like that.
also if you grep for bufferAttrib and mapAttrib in the samples/_opengl folder some more advanced stuff will pop up.