Formit and Paypal - how should I get them to work together?

I suspect I’m going about this the wrong way so I’d appreciate any pointers. I am creating a subscriber table and using Formit to capture the data - so I had in mind:

1. validate data, write to sub table
2. send visitor off to Paypal (with redirect hook to weblink resource?)
3 wait
4. process IPN from Paypal and update subscriber table to ’active’
5. leave new subscriber at landing page.

Should I instead do
1. validate data, store in session
2. redirect to Paypal
3. wait for return to specific signup page, use FormItRetriever to retrieve data and write to table

Or do something else?