Based on the previous comments it would seem that you'd still be nicely safe in the middle-white zones ?

You SHOULD be safe, but...why take a chance. Get yourself a good FFC and use it when you want a longer flying day. Higher capacity batteries will work, too. Maybe a couple of spare batteries?

Nicads maintain voltage, and maintain, maintain, maintain until !!!!!!!!!. The voltage will suddenly drop like a stone thrown off a cliff to below "safe". If the battery is marginal before the flight, it could drop to "unsafe" during the flight, and the more you maneuver, the worse it will get, FAST.

Don't risk your plane.

Dr.1