Very happy to find these adapters so 3-year-old can sit in the bigger Toddler Seat on the bottom and our 10-month-old on the smaller Rumble Seat V2+ on top.
Easy to install. Took less than 10 minutes for all 4 adapters.
Unfortunately the Toddler Seat is not reversible (cannot have toddler facing the handlebar), as this configuration causes the adapters to become loose and dislodge from its position (and you would also need to remove the basket to make room for the Toddler Seat). While our toddler would prefer to face out, we would have liked the option to reverse the seat so the stroller can be more compact when desired.
In terms of maneuverability, there was no difference with the Toddler Seat on the bottom vs the Rumble Seat V2+ on the bottom!