So, I wasn't sure if they were getting on alright.  The nice folks at Jungle Seeds told me to be patient, but of course I had to dive in and give a helping hand.  One of the paw paw seedlings had leaves almost loose, and (we've all done it, right?) I gave the gentlest of tugs to loosen them.  Well, I suspect I've ripped off those opening leaves, leaving a slightly incongruous looking bare stem.  This was yesterday, and fortunately, I think I can already see new growth emerging, so its possible there is no harm done.  I will be leaving the second germinated seed alone....definitely.