Hi, We bought our Siesta Sprinter 24SR in April. We live in Tucson and have only camped in AZ and NM. You are right, not much air comes out of those vents above the bed. If you close the louvers on the AC you should get noticeable (but not much) air flow out of both the vents.
It is just me and my wife, so we keep those vents closed and use that bunk area for pillow/blanket storage and keep the bunk floor open when camping. I put a small table top fan up there on the side to help with air movement. It has been a pretty warm summer but the AC has managed to keep it cool enough inside.
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