Yes, especially because the smaller wheels help gearing, and with the Stock-class legal adjustable dampers you can adjust for the change.
It's not just the power lost in the rotating mass, it's also a lot less weight for the suspension to control, which means better suspension response, especially on bumpy surfaces.
Don't waste another minute waiting on parts, or anything else. Just get out there and start racing! You will suck at first, and you will be slower than many other cars, but the only thing you will regret is not starting earlier...