My partner and I booked in to do the Overland in December. We need to complete it in 6 days, but we'd also like to do the Lake St Clair leg at the end (just so we can say we've done the whole thing

I've been looking at the suggested itinerary here: http://www.parks.tas.gov.au/file.aspx?id=36854 and I'm not to enthused about walking 26.5km on the final day, even if it is all easy, so I'm looking for advice for combining two of the other days. From the timelines given, it seems most sensible to either:
1: combine days 4&5 (i.e. travel straight from Pelion to Windy Ridge, skipping the night at Kia Ora), or
2: combine days 5&6 (i.e. travel from Kia Ora to Narcissus, skipping the night at Windy Ridge).
With either option we would walk the final Lake St Clair leg on day 6.
Does anyone have any comments or suggestions regarding this? Are the side trips on day 4 much more spectacular than those on day 6, and therefore we should take option 2? Or vice versa? What if instead of option 2, we did Kia Ora to Pine Valley on day 5 and then Pine Valley to LSC on day 6?
An advice appreciated!