This. Especially if you have many more trades than they do.everyone works their way up the totem pole and with the number of refs you have their refusal to ship first, without a similar number of refs, should be a big red flag. Also I had a similar issue maybe my story can help,
Had a deal for over $900 retail worth of SM
for some Dark Eldar.
He refused to ship first *RED FLAG* because he didnt want to get screwed out of so much value.
So I suggested we ship in smaller pieces, he sends whatever he is comfortable with, then upon receipt I send an equal value sure it adds to shipping but how much is peace of mind worth to you?
He again refused & later was banned for scamming.
So for fututre big / somewhat sketchy trades just do it in a few pieces this way if it goes south you have minimized your losses and never be afraid to walk away from the table if you don't like the hand you're looking at.