Using ALL of your CPF for your housing will mean that you will have:
1. No buffer to maintain the instalments when your income shrinks.
2. Lost interest income on OA balance, which you would have earned if the savings were not taken out from your CPF account. (CPF Board)
3. Principal CPF amount withdrawn for your property PLUS accrued interest, which you would have earned if the savings were not taken out from your CPF account, refunded back to your OA upon selling. (CPF Board) This means you will have less cash proceeds from the sales of your unit.
4. Lost the opportunity to probably earn higher rate of return if you were to use the remaining funds to invest elsewhere through a financial adviser.
Using CPF for downpayment is one of the common choice right? ..... unless you have lots of hard cash to spare with. Investment is always like that, either you gain more or less, worst case is to lose. No perfect strategy to ensure win win situation. Anyway if u plan to sell away in 10 years time, the risk is still there, either gain, lose or breakeven.