This is a good question. We started as a full-swap couple, but we don't have any problem doing soft swap, unless there are too many rules. Like oral? I would think at least that would have to be a given. Otherwise, in my opinion, all we're really doing is "spectating". If we soft swap I would want it to be an "everything but intercourse" situation. To me the whole idea we're there is to play with others in one way or another, not just watch them play.
Soft swap can be a nice change every now and then, though. Adds some variety.
Now, we'd NEVER try to convert someone. That would be manipulating them, and that is a HUGE no-no for us.
Mr. WS