Thanks again. It always helps to hear from folks who have done something vs speculation.
I glued up a rough test frame yesterday with double biscuits, no slats. I just took it out of the clamps and it is extremely rigid. I don’t have a homemade test machine to measure force like the woodgears guy so I tested it the same way I test my welds, I bounced it on the concrete driveway . Actually I did it 3 or 4 times trying different angles to hit corners of the frame. The joints did not fail. I am sure if I did it enough I could get the frame to break, but... Yes this is not scientific and I don’t know how having louvers in it would affect the result but it did change my mind about biscuit strength...