Try using the Fumper somewhere away from the rocks. The southeast area is viable, thus. Many cleft's are there, and as a Dune fan, I thought to use the Fumper there, where no rocks were close by. Shai'hulud avoids rocks, or anything in the ground, perhaps Hai'shulud is the same. Just an idea...

(Fumper is a reference to a "thumper", a drum placed into the ground to summon a worm. Dib'maud is referencing Maud'Dib, Shani is Chani, and a Reverend Mother is a Reverend Mother. A crysknife is a knife made from the tooth of the great worm.)