[kevinrm]

If you are using any kind of loyalty point system, you are better to start from scratch and manually add their bonus points. Even if you don't use that, honestly, I did what you are trying to do and it was hell - if I had to do it all over again, I would send all customers an email and ask them to re-sign up. It took 6 months to get that all fixed, it caused me many, many problems. Yes, I used Cart2Cart, it was a fiasco.