I always put my SD footage into a 10 bit uncompressed sequence for final render. DVCpro50 is certainly better than plain DV but cheap fast drives these days means that 10 bit uncompressed is easily done and if it is just to render your final sequence, the final render file size shouldn’t be such an issue.
It certainly helps to make graphic elements and heavily grade manipulated footage looks as good as it SD can.
That said, ProRes is a better compressed alternative than any of the Dv flavours.