My hesitation would be that mushrooms produce a lot slime when they are handled and its not easy getting them to to attach to a rock- forget glue- it just does not work with the slime. Netting them to a rock is the best technique but I have had really poor luck with this technique. You can remove the shrooms and place in a tray with rubble and let them attach on their own, then glue the rubble piece to a rock. The alternative would just be to let the shrooms overtake and cover the pvc.