This is typical of the challenge facing D.C. members.
Theoretically reducing risk as your approach makes sense, particularly if you are going to invest the residual fund (after taking the tax free lump sum) into an Annuity. The logic is that you want to limit downside risk approaching retirement.
However if you are going to invest the residual fund into an ARF, then you need to consider what risk profile you might adopt in the ARF. So if you are going to adopt Risk Level 4 in the ARF, it makes little sense to reduce the risk profile running into retirement (other than perhaps trying to secure the 25% lump sum).
So my advice is to look through retirement to how you will invest the 75% and adopt that strategy in the run-in to retirement.