Shin daisu is really big. It’s okay for it to be sitting on the heri. “Some people even put it over the heri and onto the kinindatami!“. Just make sure there’s enough room on the left for the hibashi.
When doing Shin no Gyo, you must leave enough room in the front-left corner of the ji-ita for the kama no futa. If your furo is too big (like ours), you will have to move it over.
In this and regular Daisu, it’s okay for the edge of the furo to be overhanging the left edge of the ji-ita.