Hi Matthew... First of all, congratulations for making one of the most important purchases for your culinary training (next to the knife) - a stock pot. Everyone take note :-)
Secondly, I congratulate you on adapting (splitting up the mirepoix because you noticed that it was steaming). Paying attention and asking questions is the first step to obtaining the results you desire. You did the right thing.
Thirdly, I would like to suggest that you review the lesson on
Stock Making Fundamentals. In particular, topic number 5. When making stocks there are no hard and fast rules regarding the ratio of bones to vegetables. We suggest a ratio of 3 parts bones to 1 part mirepoix but this is a general guide only. For the mirepoix, half onions and half celery, carrots and leaks. So next time, forget the recipe altogether and eyeball it. If in the end you'd like a bit more chicken flavor, add more bones. Play with it.
Lastly, caramelizing the bones is important. Not over caramelizing is also important (e.g. burning). So you did the right thing to trust your judgment. The subsequent lesson in the Stock Section on
How to Make Dark Stock will provide some great technique for you.
Great work. Try another small batch after you review these lessons and then let's make something with it. If you need suggestions, click on the 'Contact Us' link on the bottom of the page and we'll suggest a few great starter recipes.