When I'm playing a passage fast, and I need to jump quickly from D2 to C#2 and back to D2, I'm finding that if I use the fingering for C#1, it's so much quicker, smoother and frankly easier. It sounds more fluid to me, and the C# I get by using the C#1 fingering sounds about as good as it does if I jump up to play the C#2 fingering "correctly" (in fact, to me it sounds better - without the big discontinuity, I can play much more fluidly and the note seems properly connected).
I think my old flute teacher would admonish me for "cheating" that way and insist I play C#2 using the proper fingering. But she's not around.

My question: when I'm playing D2 and I need a quick C#2/Db2, is it really so wrong to just press down that big, flat C#/Db key that's right there next to my pinky if I need a quick C#2/Db2 (even though all the fingering charts tell me that I should just lift up every key finger and play it with nothing but the ubiquitous D#/Eb key held down for stability)?
Is that "cheating" or just an alternate fingering?