I spoke with Computershare on the phone just then.
My circumstances are that I sent the form accepting rights and applying for shortfall. I set up a bank transfer to pay the money.
They said to fill out the form again with all the details on the original form and with the extra shortfall amounts included. Then, I could email the form to
[email protected] and as the subject like have "New Talisman Gold Mines NTL Form XXX" where XXX is the initials of your name.
They said to note in the email that I had already applied/sent in the form/paid and that I wanted to use the newly filled out form as my application.
They said to top up their bank account with the additional funds, including the same reference numbers.
So there you go - they said I could apply for more.