What a gift of a day... In fact the best I've had in southwest Tas. Here is some info that may help others looking to do Fed in a day.
Access is as described in John Chapman's guide. The logging roads from Tahune are currently in good condition, easily doable in a 2wd. Farmhouse creek is easy to find and there is space for around 8 cars at the trailhead, with more further back. I left the car at 7am, half an hour after first light.
Short and long term weather conditions were very good. Two large stable high pressure systems lingering either side of Tas for the long weekend, preventing most of the inbound airflow to the southwest ranges, reducing the chance of precip - though this area can famously turn at any time, the forecast was promising. The summer had been dry, with historically low rainfall. I had never done Fed Peak, but previous experience in the southwest had been mud to knees/waist, particularly the buttongrass plains. I was pleased to find mid-calf mud at most, and long sections of the plain actually runnable. There'd been some rainfall the previous week so there was at least some water in the creeks. Conditions were excellent. This should be noted when comparing times between attempts, and I'll be quick to add that Hanny/Dale's FKT looks to have been done in far more difficult circumstances. Doing it in a day is a challenge and I think that should be the benchmark, rather than splitting hairs on times.
Despite the good weather, the route was, of course, still difficult. I think it's helpful to divide it into 3 sections.
1. Farmhouse creek to Moss ridge (18km)... cover this ground quickly. Sections of difficult terrain (forest, roots, mud - see various youtube vids), but some fast sections of trail, particularly the first 5km from Farmhouse. Gentle rise over a densely forested ridge, then approx 9km of buttongrass. There are multiple water sources en route. South Craroft was stagnant, there were cleaner streams between the slight rises around 12-14km. Significant fire damaged areas. Route finding was straightforward.
2. Moss ridge to the Berchevaise plateau (about 3km horizontally, 700m gain)... aim to climb efficiently, through overgrown/thick trail. I did very little running on the ridge. It's a hike. Steep forest, thick growth, tree climbing experience would be helpful and a large pack would be a hinderance.
3. Fed Peak proper (about 1km of scrambling, 300m gain)... the challenge is exposure, and a little route finding. It's well documented in the guide & online blogs - head up from the plateau, over the col, descend a rocky gut, sidle skier's right to the main access gully, up under the chockstone, then spectacular scrambling up the face above Lake Geeves. If you are confident with exposure, and have some very basic climbing skills this is the jewel of the route. The climbing is not technical in a rockclimbing sense, it is exposed scrambling. I would grade it at UIAA II(+), YDS class 4 in the hardest sections. Cairns mostly mark routes up the face but some route finding is required.
My approach... Running gear was merino based with trail runners. Lightweight waterproofs, a light mid layer, beanie/glasses/cap. Emergency supplies, and a small medical kit. Food. Running pack and soft flasks. Garmin inReach and a phone. Tracking on a Suunto 9 baro, with inReach backup. A plan to turn at 6hrs given I was solo. I reached the summit just after noon, ahead of schedule, and spent around 20min on top. Approx 5hrs out, 6hrs back. I suffered in the heat on the return... but Farmhouse creek is good for a soak at the end.
The major risks are the usual for the southwest... Remote, difficult terrain, unpredictable weather. Add the exposure on Fed - which many will enjoy, but some runners will not. There are unique challenges to doing it in a day... picking the conditions, having the legs to get out there while having the head/experience to climb with a margin of safety (while tired). It's a big day, but there are at least 8 I’ve heard who've done it, probably more. HIGHLY recommend, and happy to chat to anyone looking to have a crack.
Note: check yourself for ticks, I picked up a passenger (ixodes holocyclus), didn't notice it for days. Apparently they're out in numbers this season.