This boat is definitely built for sailors who want to use the aft cabin for sleeping rather than the v-berth. We have a fan mounted next to the closet that does help a lot. I always have the hatch open and both ports open. Sometimes, I will raise the cockpit seat just so I can open the hatch fully. Does your model have a hatch? You didn't mention it.
Our A.C. compressor is in the cockpit locker so it is too noisy for me when sleeping. Sue doesn't mind. We have rarely tried to sleep with A.C. and only when Sue is on board. I don't even like fan noise in the cabin so I will usually turn it off when I'm alone just before going to sleep. Sue needs white noise so it is always on for her.
If you don't have A.C. I suggest trying to find a better location for the compressor if you want it, unless the noise doesn't bother you. The aft cabin has an A.C. vent but it does not cool off nearly as well as the salon. I always close the v-berth when using A.C.
I have no problem dealing with the heat overnight when I'm alone, but I'm sleeping under the fan at the front of the cabin. Sue is claustrophobic so she has to sleep next to the door. I'm not claustrophobic, but I'll admit that it feels too close for comfort at times tucked into the rear corner when it is very warm. On rare occasions, I'll sleep in the cockpit to cool down on really warm nights. It's also an option for me to sleep in the saloon with the A.C. on (it's less noisy) while Sue stays in the cabin.
To make a long story short, the aft cabin can be a bit stifling on really warm nights, but I've been able to deal with it and 90% of the summer nights (July & August) I'm perfectly comfortable. On anchor, without A.C., I've never been too uncomfortable with the heat. In the marina, where there may be absolutely no breeze, is the only time I've had to adapt. As always, YMMV, especially on the Chesapeake.
I like the aft cabin arrangement more on anchor because it is quieter than the v-berth. In the marina, I can get annoyed when the ripples slap under the stern when the breeze is facing the stern.