Very sound advice from Tex, he is truly a Drifter-file, I recently did a trip here in Aus from Adelaide to Avalon for the air show. I have a 582, I have just a 65 litre tank but supplement that with 40 litres on the backseat, a 12 volt low pressure pump that transfers the fuel through its own filter to the main tank where the engine draws fuel from. I have two system to confirm fuel level prior to transfer, a fuel guage with a mark at 20 litres so there is plenty of room for the 40 L to go and a mirror and a sight line on the side of the main tank. Confirm there is enough room and then transfer, takes about 18 minutes and I'm goog, gives me 105 L of total fuel on board. If the fuel transfer fails either before or during, I'll have a minimum of 45 minutes to find an alternate landing area to resolve the issue. I found 4 - 5 hours at one time is heaps of flying, maybe do 3 in the morning and 3 in the afternoon, remember to hydrate and keep your food intake light but often. If you have too a bit of Avgas is ok, I have done it once or twice just costs a lot more.