6A FI =Mixture Cable length?

I have been searching the posts and they are all over the place on length. What have folks used for a mixture cable length for a 6A RSA5/vertical induction FI setup?

Vans has a mixture cable for the 6a which is 45in but I'm concerned that it will be short.

Thanks,
D

The RSA5 that I am installing is a experimental from AFP. (FYI: Don @ AFP is awesome!)