Hi Ed,
I'm 56 and thought a single day was fine. We started at 11:30 pm and hit the Cockstone at first light (7 hours). We summited around 3:00 pm (16 total hours) and hit the tram around 6:00 pm. One of our party was a 29 year old Navy SEAL and he topped out in about 14½ hours. This route adds about 1½ miles and 500' of gain/loss compared to the illegal route but you can legitimately claim a 10,000' day.
The parking is located in a lightly populated neighborhood and adds a big bonus for car to car camping or efficiency for descending skiers and snowboarders.
All that said, there's little time to spare, so a single day attempt could be an issue if you get off trail and aren't using the track for navigation. I think the best way to avoid an epic is to go up late in the winter to Falls Creek (6 hours), assess the snow accumulation and camp. I'd go light and fast from camp to the Chockstone and understand that all of the 5 miles from car to Chockstone will be done by headlamp on game day.
I've camped at Falls Creek a few times. I enjoyed the scenery, took in some bouldering and the recon made me feel better about the event.
A two day with a camp near the drop-in entrance to Snow Creek would be fine as well but that extra weight!
https://photos.app.goo.gl/9FdTg2TnpKDJwuXA8