Hiya,
Further to Geoff's comments, if you record a loss in your trust then you cannot claim the franking credits in your personal return.
You need to distribute a profit in order to do so.
So, if your shares are geared and your other expenses (travel, gifts, stationery, etc) exceed the net result from your shares, then you would have a loss and thus lose your franking credits.
But, if you had a HDT and geared through your own name, then provided that your income was greater than your expenses, you could still negatively gear the interest in your own return, and claim back the franking credits...
Cheers
James.