I read all incoming full manuscripts on my Kindle.
That means I request all manuscripts in .doc form.
That does NOT mean you need to reformat for what you think is the Kindle size.
Just send it as usual: one inch margins all around, 8.5 x 11 paper.
The Kindle does the adapting.
Add this to the list of one LESS thing you have to obsess over when sending work to agents.