Although square plan dome tents using flexible poles were available at the time, they were problematical for serious mountaineering because the volume of excavation required on steep snow slopes was excessive and for an exhausted party, often dangerous. Also, The geometry of square plan domes is conducive to easy deformation in high wind, necessitating guys at 45 degrees - very difficult to guy the outer poles on high snowslopes - whereas the fore and aft guys on the tunnel tent are easy and almost eliminate excessive deformation.