I use a 1" hose. It fits tightly in my 5 gallon carboys and I don't lose much to blow off. In fact, some of what I lose is future trub; mostly hop particulants, heavy fats, proteins as well as some beer, depending on how active it is. Ideally, use a 1" hose and a 6.5 gallon carboy for a 5 gallon batch. If you do a 6 gallon batch in a 6.5 or a 5 gallon in 5 gallon carboy, that carboy cap and tiny hose is going to hit the roof

The caps are nice in place of an airlock, but not really in place of a blow off tube unless you have a lot of head space (and don't need a blow off tube in the first place).