I would look at the plastic construction and maybe go through the UL file requirements for that plastic.  They are probably the answer on what the flammability rating would be with data to support it.  Maybe looking at the UL tests you could find reasoning that your customer would accept.

Interesting problem though.  We don't currently have products were pin to paste is possible due to several factors so I have not had to look at components for this recommendation.  Are component manufacturer's testing and making recommendations for pin to paste processes (other than this part) or has the industry missed the boat and this will become a larger issue as the technology grows?  

Kathy