The scaling is probably the reason you have to render DVCPro5r0 is 720×480. For widescreen it needs to be anamorphic, not 1280×720. Another reason to use ProRes – it can be 1280×720.
I convert all non-standard codecs that come into the shop to ProRes422 before editing. And no rendering is needed until you apply filters, etc. to the point your system can’t keep up. With terabyte drives costing $85 there’s no reason to worry about file size. You should try ProResLT which will produce smaller files than ProRes422. You could even try ProRes Proxy and see what you think image-wise. Do not use ProResHQ.
I’ve converted many Flip HD clips to ProRes and they look a lot better than I expected.
John
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