I think my just over 4mth lo is heading that way too- she only takes about 3.5-3.5oz each dreamfeed and even if she does wake up, she'll only take another extra oz or so but even that's a bit of a stretch. However, I'm too much of a scaredy-cat to experiment letting her sleep without! During the day, she takes about 6-6.5oz per feed (on 4hr routine) and she seems pretty content w/ that.
I think that if your lo only takes 2oz for dreamfeed, there's no point adding the extra oz during the day feeds, unless of course she's hungry for more... By the way, what time do you give the df and what time does she sleep until?