Hey Pete,
Unless it is progressive scan, I’d avoid rendering in that mode from Vegas itself.
And John is correct on the size front, obviously that might be a problem for you too if you are doing anything flashy with the graphic.
Personally I alway render at best quality, even for web based jobs, best to render out from the NLE high and then down sample later IMHO.
Another wee tip for the record is VirtualDub which has some great resizing as well as deinterlacing options, plus its free.
Vegas pre version 9 can frameserve directly to it using the free debugmode frameserver which is great for keeping the highest quality whilst converting mixed field media to a progressive stream if thats the way you wanna go it.
Unfortunatly I don’t think there is a working plugin for ver 9 yet.
Best of luck
Pete
http://www.nexusdigitalmedia.tv