Congrats on the new car!

If you want to try to prevent regen you could try PnG on the flat,
meaning get up to speed, or a little over, coast in neutral, repeat.
PnG is a perfect pack drainer if you use assist on the 'P' part.

If the flat is a high-speed area then shifting into neutral may not
be practical since shifting back into drive might reduce CVT life.
If there is a jerk when you shift then you know that wear-and-tear happened.

I have a 2000' ft climb I do frequently, and I doubt you will ever get the pack
low enough to avoid it going full on the downhills. :-)

Best round trip mileage I ever got on that hill was 45 on a hot summer day.