You are an experienced rider so I take it you will drink and graze during the ride. But one thing I would do from now on is Carbo load. Plenty of pasta and rice for the rest of the week. Day before the ride drink a couple of "Extra" litres of water and before the ride starts drink some more.
I did a ride yesterday and in 5 hours drank 4 litres of water- had food on the ride and a good B-B-Q afterwards Today I have not stopped drinking and I am hungry. So pack Fig newtons- Dried fruit-some cake- and anything else you can get in your pockets to keep the energy up for the 2nd day.
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How long was I in the army? Five foot seven.
Spike Milligan