ellaroo wrap ?

TabithaGoins

I'm looking at buying an ellaroo wrap and have a couple of questions.  If you have one, are you happy with it and does it work well for older babies.  My son's almost a year and 19lbs so he's on the smaller side.  Also, they have sizes..would it matter if I bought a size up.  For instance if I "should" need a 4.6 but purchased a 5.0 one, would it still be okay.