its not 2-3 day guaranteed. its not late unless its i think like 14 days or something. yes most all packages get there with in 2-3 days but there no guarantee. i use the same 7x7x7. by the time you add heat packs now its going to be over the half a pound. i dont think i ever sent plants first class before.I use priority - 2 or 3 day delivery guaranteed.
I use the VCR and Large VCR boxes. Bigger plant packages, use a bigger box....nothing hard here.
I don't mess with first class because people are always whiling to pay for priority I will agree that first class will get to many places in the same amount of time as priority, but that isn't the case for things places on the coasts (I live in the midwest)