Irrespective of selling an investment you can make a contribution and receive a tax deduction if:
you are fully self employed OR your income from employment is less than 10% of your total income (investment income >> earned income).
It will still be taxed at the super fund rate of 15% going into the fund. You have to write a letter to you super fund.
I don't know, but I doubt you can "save on capital gains" as such. My wife and I have been fortunate enough for our unearned/earned income to meet the requirement in recent years, thereby reducing income down to the 15% tax rate. Effectively this is saving on capital gains.
