Extra large battery

The CAPACITY of the battery is immaterial as long as is not too small.

You can't have Too Much capacity until the weight becomes an issue.

It is still 12 volts no matter what the amperage rating is.

Analogies...

A car might have a 400hp engine but that does not mean you can't drive it at 20mph through a school zone.

You can plug a night light into your house that has a 200 amp service panel and it doesn't go up in a fireball.

The Ampacity of the battery is what it is capable of delivering, not necessarily what it is going to deliver.

Feel free to install the largest battery of your choice.

if you have the possibility, it would be good to move elements to make the rear of the plane lighter

Unfortunately not an option. I have already cut weight and nearly halved the nose ballast as is.