It's definitely nice work shoehorning all that into a BMW frame. But if it gets 83mpg, wouldn't the original tank get you over 400 miles?
Maybe the other tanks are for the bio-D.
With no saddlebags, it would seem to be relegated to city commuting or hack duties...
Current: 93 R100GS, 04 XR650L
Prior: 73 CB350, 77 R100/7, 83 R100RT
I love every motorcycle I've owned and even some that I haven't.