Nothing is going to float motionless up there. The idea is to keep it within a certain space; I believe GTE is trying to stay within a 1 mi radius of a point and in Vern's infamous post on RB he said it would fly something like 10,000 mi to maintain that position for a day (don't remember the exact number). So something that flies like a plane (and perhaps glides like a glider at times) could do the job.
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