The Touratech Xchallenge tank is huge too. But on a bike like the Xchallenge it makes sense to have a decent fuel range. although they do like 25km/l or something. So on like 30 liters you could probably do about 700km.
I have a couple of mates with them and they often travel into malawi/mozambique and even further up into africa.
Ex SM610, FS570, WR450, Africa Twin(s)