Sholom Rav,

The Rashash's question, as you clearly imply, is non-existent - according to the diagram in the latest versions of the Gemara, which is what you obviously use.

However, if you look at the old versions, you will see that the over-lapping Kuchin do not reach half-way along the adjoining Ma'arah - which they ought to (as the Rashash points out). Clearly, the producers of the later versions took the Rashash's Kashya to heart and corrected the picture.

Be'Virchas Kol Tuv

Eliezer Chrysler