In rav ashi's answer why did he have to change the case to a doorstep of is a house let it be the same case ie a mavoi and 2 korehs less than 4 etc can still work on this case.basically whats the n.m between askupat mavoi and askupas habais?
y kaplan, johannesburg, south africa
Rashi explains that the entrance to a Mavoy is usually not covered.
One does put a Korah over the entrance in order to permit carrying in the Mavoy, but the width of a Korah is normally not more than a Tefach. In addition, a single Korah would be used and not two. It is not likely to find a Mavoy with two Korah's placed as you suggested. That is Rav Ashi describes the case as Iskupas Bayis.
Mordecai Kornfeld
Kollel Iyun Hadaf