I will answer 2 ways:
1. (Assuming you have a CC Permit) Knock yourself out. Carry how ever you want.
2. (Assuming you don't have a CC Permit) Be careful. An IWB Holster is by definition designed for concealled carry. As you describe it one "could" say that was open carry. However, let me describe the most likely LEO encounter. LEO would assume that you were intending to carry concealled and that your sweatshirt just got accidentally pulled up and over the gun. They will likely point that out (as a courtesy) and then ask to see your permit (just for good measure). At this point if you don't have a permit and you try to claim that you were intending to carry OC is going to sound like a load of crap.
Just my $.0.02