They will be plenty warm enough this time of year. Alternate your frames of foundationless between drawn frames, this will encourage them to draw out the foundationless frames, and they will be drawn straight.
The center of the broodnest is the most critical in acquiring smaller cells. Keep feeding the foundationless frames into the center of the broodnest and move the frames with the larger cells toward the outside, and as you add another box on top, move the larger cells up top, feeding more foundationless frames into the center of the broodnest.