Hello - I got a Radwagon 4 from my husband for Christmas. One big reason I wanted an e-cargo bike is to be able to take our dog, who is 38 lbs collie, places nearby like the park or to appointments as needed.  He has experience riding in a Burley Tailwagon but I dont' want to have to store that thing and hook it up separately anymore.  I have seen examples online of people strapping laundry baskets or heavy duty storage boxes to rear bike racks.  The large bike basket from Rad isn't big enough for him, I don't think, esp as I'd like him to be able to lie down somewhat.  Rad has cautioned against using the caboose and putting in something like a box or basket but it seems like it could work well to me.  Otherwise I'm not sure what the safest way to attach a plastic or wood box would be?  I found some attachment pieces for milk crates on Etsy, but a milk crate isn't big enough either.  Ideas?