Not done any audax's yet as my location makes it tricky and expensive ,but I did do my first 204km ride the other day(solo) up here in Shetland. 10hours total, 8.5 moving.https://www.relive.cc/view/994273297http://moder-dye.blogspot.co.uk/2017/05/nice-day-for-long-ride.html
There are a few in the NE Scotland area I could make and fancy,but its the 12 hour ferry and cost each way that's off putting.
It was a struggle towards then end of my 200 and the next step of 300, never mind 400 or more seems a long way off. But I'd like to.
Any tips for the next step? Plan an easy route, wait for good conditions? Ride slower still?
As in the nausea and food thread I couldn't put anything in my mouth other than liquid for the last couple of hours and lower intensity and more savoury snacks were suggested, but as well as that getting to 300 would involve the legs managing more hills, they're not monster hills, but there's not much flat and we do have the odd breezy day, even on a calm day