Unfortunately, I don't think this would help me achieve getting my arrow at the right angle.
A Euler spiral is definitely the way to go.
Anyway, I've spent quite some time and I've amassed the following formulas:
Xc = (Ls/100)*(100-0.0030462*θs2)
Yc = (Ls/100)*(0.58178θs-0.000012659*θs3)
θs = Ls*Dc/200
Dc = 200*θs/Ls
Dc = 1800/pi/Rc
I know Xc and Yc and Rc but I need Dc.
So I'm hoping I will find Dc if I rearrange the formulas.