I think a lot of it depends on how much you've paid for the jiffy bag in the first place. Jiffy is a trade name as I'm sure you know, but very few padded bags bags I see are actually made made by them, which have a shredded fibre padding as opposed to a bubble wrap. Bubble wrap lined bags are made by people like Sealed Air, Bubble Lined, Air Pro, - there are loads of them. But I always buy the "plus" versions which have a much thicker "outer" to them. A lot of the problem is not necessarily to do with the padding on the inside, its to do with the envelope that holds it together on the outside.
If the pen I'm sending is in a hard case of the sort that holds the pen securely, I'm perfectly happy to send it in a "plus" grade of bag, even overseas, without any extra protection at all. If the pen is not in a case, I have lengths foam edge protectors for furniture. It's an L shaped profile, which I cut to length. Pop the pen in a sleeve and then inside the foam protector and squeeze the two arms of the L together. Put a rubber band around it, then put the whole thing in the bag. Job done.