We have a 2922KB, and I will say that the back king bed is much colder than the front full size bed when using just the TM furnace (which makes sense because the furnace is in the front part of the TM). If we're boon docking, I use a small rechargeable fan clipped to the bathroom walls to move the heat from the front to the back bed.
When we are on shore power, we use two of these -
https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1 - one for the front bed and one set by the wardrobe cabinet for the back bed area. These keep it very toasty for both front and back. I also use the furnace when we first need to heat up the TM quickly.
Also what works well is having an electric blanket for the king bed, assuming you have shore power.
And I wish there was a way to leave the bathroom walls down sometimes - it would probably keep the back and front heated equally if you don't need the toilet, BUT because the walls being up enables the propane/CO2 sensor, you need to keep the walls up to keep you safe.