Thanks for the replies,
Yes my wife will use it on occasion but that would only be sitting out back taking pictures of squirrels and hummingbirds. She has no qualms about the weight of the 70-200L but does prefer 70-300L.
Maybe a tele is the right choice for short term and look into a used prime. I have considered the 400MM 5.6 but the MFD and lack of IS was a deal breaker.
Living in Seattle we are low light shooters 250+ days a year so IS is important to the types of shooting we do.
There is a local rental store to get both the 1.4 and 2x tele convertors. Maybe I should try this for a weekend.

Again thanks for the input and ideas.

John