i'm not sure the size of the bag matters? we've been to DLR 100+ times in the past 8 years, and rarely have we gone without bringing in some kind of sandwiches or snacks, bottled water, etc. (we have 4 kids so bringing in healthy snacks, water, and fruit is a must for us). we carry the Ascot insulated bag now, which i mentioned is about the size of a regular backpack. but for probably, oh, 7 years we went in with a typically sized diaper bag. never ONCE, have we had any problems bringing anything in, whether it was just granola bars and apples, or whole sandwiches. the routine at the bag check never varied at all either, regardless of how big/small the bag was we were bringing in.