I used a large heating pad (12' x 24") for the cave, and moved my 3 week old chicks to the other side of the brooder so the newborn chicks could use the Sweeter Heater. Newborns adapt to the SH immediately. The older chicks were a little leery of the HPC, but went to it as soon as the lights went out. I eased down there about 30 minutes after lights out, and all 15 were snuggled down beneath it. It appears to be working perfectly! I think I've found the perfect solution for staggered hatches (or should I say different aged chicks?).
All the chicks looked happy and healthy this morning!
Thanks for the compliment, and thanks for asking!!!