Should I downgrade the NTUC Income ISP?

Planning to downgrade my existing health insurance plan. I am 31M with no pre-existing medical conditions. For policy renewal the cash outlay for Plus rider for Enhanced income-shield preferred policy is $981 for zero copayment.

I am thinking of downgrading to a policy with 5% or 10% co-payment while retaining the private hospital coverage. While I have no difficulty in paying the premiums, I was wondering whether it would be a better idea to downgrade and invest savings from the premium.