Hi,
The super roles are changing next financial year, which means that people won't need to salary sacrifice, but anyone can make a tax deductible contribution. Much easier, transparent and user-controlled than the archaic salary sacrifice situation.
Sadly, it only starts on 1 July, so for this year you are stuck with salary sacrifice and all the issues it has.
I've been caught by the timing of payments from my employer (the cap is based on when funds are received by the super fund, not when they are "earned"). Hence them being slow with a June payment resulted in me exceeding the yearly cap in the following year, and paying the penalty taxes.
Next year, wait until May, figure out how much headroom you have left in your $25k, send the money yourself to your super fund, and claim the tax deduction.