I'll let others who are better versed in this subject debate the merits of one type of shelter over another. My point was more that we may not always have control of our circumstances, and should be prepared for different eventualities. I'll go out on a limb and state that I believe the OP is aware of this as well, and is looking to expand his knowledge base to cover more than one approach, hence his asking for info on expedient shelters, rather than whether or not he should BO or SIP in different events.
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