Bad idea...
I suggest you use an OMM for this large of a trade http://www.sythe.org/middleman-forums/1302647-official-middleman-list.html
Okay, so lets say I use omm? Do we both send it to him first?
I don't really have that much experience with these types of trades, but I'd assume so.
I don't think that, I think that what the MM do is tell them send both items to each other and make them send him the tracking number so he will know if the items got to their address.

