Scratch stock blade

I am doing a restoration on a house that was built in 1908. On the porch, one of the the top and bottom rails had rotted out completely, at the ends. Needless to say, they are not your everyday railings, you pick up at the local home center. I have managed to fully restore both rails, using a combination of wooden planes I own.

I have one last detail to put on the top rail. In order to make it correctly, I will need to make a scratch stock of the correct profile. My question is, can I use plain sheet metal to make the pattern? Will it need to be heat treated? Would I be better off making the profile out of an old hacksaw blade?

Thanks

Dave