I'm not sure if i know exactly what you're trying to do, but if you are trying to fit 4:3 images into a 16:9 project, how about setting the project properties to 16:9 and then using Crop to trim the source events to fit? This seems like it would be a lot simpler and easier than exporting frames.
I understand "match output aspect" but I get really frustraed in VV which seemingly has no "free transform" feature. is there a way to qucikly resize any graphic or clip without having to switch tons of settings on and off. Im alway left jumping between Pan/Crop and Track Motion getting confused with the settings. In all other programs I can just hit "transfrom" or "scale".
example, someone on a FCP forum said "try scaling to 133%" ...well, in VV its not obvios how to do that. Suppose I want five clips to fill the frame, I ned to easily change there sizes without VV grabbing. I even sill have trouble bring in oversized iamges and keying them around the frame because it seems like VV grabs them and I have to go through an arcane process to stop it from doing so.