Transfer SG stocks from IBRK to CDP: for DCA SG stocks, advisable to buy using IBRK and then transfer to CDP account?

If I plan to DCA every 3 months into SG stocks, should I buy the stocks using IBRK account to take advantage of the lower commission fees, then transfer the stocks out at the end of 1-2 years to CDP so that I only need to pay the $10.80 once a year as opposed to every 3 months? (Supposedly, having SG stocks in CDP is safer…)