Five item trade window for armor sets to avoid scamming?

[Tameron]

Twice now I have been involved in what I would describe kindly as misunderstandings, while trading armor sets whole. Armor sets are five items, and the trade window only holds four, so usually people just give an item either before or after... But I just got stiffed for the fifth item in a set (something I was one accused of myself, though that was resolved amicably by a mutual friend) and now I have to either track this guy down or bring in the guard or worse, the devs with reports and stuff, which I don't want to do.
Improving the trade window might be a lot of work, but is this a significant portion of trade disputes? Might be worth the time it takes...