Well we have different breeds. Mine is a Jackson's Xantholophus. I don't know how to compare sizes between a Xanth and a Panther. My boy is going to be 7 months old on the 16th of September. Regardless of size your baby should be eating 10-12 feeders a day. Also so long as he is eating, pooping and growing I wouldn't stress too much. Just keep doing what you are doing, the feeder run should help a ton! Smooth out the edges of the home-made run so baby doesn't hurt his tongue on the sharp edges.
Here is a pic of my boy now, he is still quite small compared to my adult panther but he is growing well.