C152 flight Instructor reported a ground conflict with the preceding aircraft as the aircraft turned on to the departure runway. The departing aircraft's right wing came within 5 feet of Cessna 152.

Narrative

My student and I requested taxi clearance from the Company ramp. We were given clearance to Runway XXL via X and were instructed to hold short Runway X. After being cleared to cross Runway X; we were instructed to continue our taxi to XXL via X. We usually stop at the XXL run-up area just south of Taxiway Y; however the pilot of a an experimental tailwheel-type Vans RV6 had positioned himself such that we could not enter the run-up area without receiving the full extent of his propeller wash. Because of the RV6's position; I elected to conduct our engine run-up while holding short of Runway XXL in the interest of safety; as I was unsure of how long the pilot would need to conduct his engine run-up. Approximately 5 minutes later; the RV6 informed the Tower his run-up was complete and he began his taxi towards XXL for departure. However; the pilot was unaware of our position for an unknown reason and; due to the low forward visibility of his aircraft; came within 5 feet of our propeller as he entered the runway. Had he come any closer; his right wing would have collided. Due his lack of visibility and our orientation in relation to his aircraft; I could not take any evasive action; as doing so would have led to a collision. I informed the Tower of the near-miss and after several minutes to recollect ourselves; my student and I elected to continue the flight.