Yeah I can answer this one.
Access is by Snowy Creek road, turning off the Alpine Road to the east, just after Tawonga Gap road. You're right to follow that down to Dungey Track in your car, and then keep on Dungey (a bit more slowly) until the turnoff to Stony Top Track, at about 700m ASL. This then goes up to to Dungey Gap at 1300m , about another 10km down the road. Your info about the seasonal closure was off - it's not 14km back from the trail head, but rather at Dungey Gap itself. Another 3km or so after this, the Stony Top Rd ends at the trailhead, and you have a further 4km to Feathertop Summit
Now, stony Top Track is the main (ie only) vehicle access track, and while it's open to Dungey Gap year-round, you're gonna need to be preeeetty brave to get your hatchback to there. Which leaves you a good 17km or so to walk from Dungey/Stony Track junction to get to the Summit, summer or winter. To add to that, the only (semi) reliable water is at Dungey Gap too, in the form of a teeny little creek and a fire water tank.
The last k or so up to the feathertop summit is steep, too. Not quite MUMC/West Face steep. But don't go trying to do it in July with sneakers on, and allot some extra time for it.
As for champion spur, yeah - it's a slog. or an adventure, depending on your attitude. It's basically an exercise in off-track orienteering these days. Not hard mind you - head west, go downhill. But in snowshoes it could be...tedious. Especially if you've just walked 17km up Feathertop. Oh, and the bottom of the track puts you into a river valley with some crossings, so be prepared to get yer feet wet.
My advice, given that you have to park at the bottom of Stony Top Tk?
Doing it in summer - go hard and go light. Ditch the tent, take a tarp and a tin stove in case you need it, and get walking up Stony Creek Track before dawn on day one. If youre fit, you can be over the summit after lunch and down in Federation hut for the night. Then you have the whole day to flounder down Champion Spur and hate yourself the next day.
Doing it in winter? Allow 3 days. Snowshoeing 15km uphill then having to summit kindof takes the fun out of summiting, and late and tired is when people make mistakes. Go for a tumble off the northern approach at dusk, and nobody's gonna see you do it. Camp at Dungey Gap, or further along if you can find a flat spot (there's a few here and there, more above the treeline as you get close to the final approach). Then do the summit at your leisure in the morning on nice re-frozen pack, and either lounge around in Federation for the rest of the day, or walk a few more k's and camp at the head of Champion Spur. Then you have the whole of day 3, to flounder down Champion Spur and hate yourself.
If you want to do it in two days in winter, you're gonna need to get drop-off further up Stony Top Tk than your hatchback can take you. Bribe a mate with a fourby.
Oh and lemme know if you do decide to do this in winter. If you're after a hiking buddy, I'm keen (no 4wd though

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