Adding the additional fields to the web.config and dni_clients tables are all that is required to add access to the additional fields in the code. Below are some primary places in the code where the profile is accessed. You'll only need to add your new fields in the places you want access to them.
account.aspx
admin/client/edit.aspx
admin/invoices/edit.aspx
admin/imports/clients.aspx
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DotNetInvoice Support
support@dotnetinvoice.com
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Rob
DotNetInvoice Support