As you get more comfortable with your PBC you will find the intake opening to not be as important to your cooking. The exhaust - which is the annular space around the rebar - has more to do with raising or lowering your temps. If you need to raise the temp. quickly - and be careful with this tip - you can fold up a small piece of foil and place it in between the lid and the barrel in order to create a small gap which will allow air to flow thru the pit faster. That will cause the charcoal to burn hooter - so - again, be careful because you can run the temp up 50-75 degrees pretty quickly, depending on the thickness of the folded up piece of foil.
Keep up posted on your progress!