I'm sure it helps some. I just think the safe thing is to know your pad has the right R value for conditions and not rely on anything else.
With comparable quality, a quilt will be lighter and cheaper than a bag, but not everyone will like it. There are hybrids that fully unzip to quilt mode, too.
I liked my Feathered Friends quilt at Philmont this year. It was actually warmer in quilt mode than in bag mode.
Who would have thought that not following scouts was unusual.
Tell your scoutmaster that just like the scouts have to learn to make good decisions, adults have to learn how to stand back. It takes practice.
Reminds me of a parent waiting to ask me a question after a troop meeting. At least a half of dozen scouts swarmed me, each needing to ask me their important question. The adult finally slotted in and asked me how I manage to respectably give each scout his time in the middle of the chaos. My quick answer delivered with a laugh was "Practice".
The adult leader job in a troop where scouts are given the freedom to make bad choices is the hardest job in scouting because every sense in their body is telling them to do otherwise.
Was talking about this topic last night at the meeting. SM is having a hard time sitting back and letting the Scouts screw up. But he knows that mistakes are the best learning opportunities. I told him that it was because the adults did not follow the Scouts at camporee and coach or tell the Scouts how to do stuff that most impressed my wife. Watching the troop in action removed reservations she had about them.
As for the original question/costume. I would not damage a good shirt that someone else can wear. Maybe hit up the Goodwill's or other thrift shops and see if you can find a cheap alternative. Maybe a Dickie shirt.