I mix foundationless frames in with foundation frames all the time. I never had a meltdown because I always keep on vented supers between the inner cover and top cover - to keep a good convection current going. In the dead heat of the summer, I pull the slide out of the screened bottom board to help with this. I have this vented super on all year long. (But in the winter, I plug up 6 of the 8 holes to prevent downdrafts. This still allows warm, moist air to escape. I never have a moisture problem.)