It seems to me from what I am reading that the float arm adjustment is not the issue, you are all complaining about the inability to use all the fuel in the tank. Looking at the PDF the issue would seem to be that the pump housing is not reaching all the way to the bottom of the tank leaving the 20 odd liters unavailable. I also don't like the way they are indicating to make the float arm lower than the pump pickup point, that could lead to a burnt out pump. This will also not help with the fuel level reading as the sender arm will hang in a space well below the final pick up point instead of reading empty with about 2cm of fuel left in the tank (see image below for clarification). Or at least enough fuel for the pump to scavenge 20-30km more fuel before sucking air.
I haven't looked in the workshop manual to confirm but I would assume the pump will sit inside a swirl-pot, any decent aftermarket tank manufacturer should not only have baffles but also replicate the swirl-pot for the pick up.
With previous issue's like this I would simply extend the pickup pipe, cables and the pump bracket on the pump housing with a custom made bracket. However if the photos are accurate then the pump housing is plastic and no longer steel, this makes it harder to safely extend the pump using a custom bracket as unlike a steel housing you cant cut and weld. The photo in the PDF has rather conveniently covered the area we would want to look at to asses if its possible to safely extend, unfortunately the image in the manual does not show enough either, anyone have a photo of one pulled out of the tank?
The real issue here is the manufacture of the long range tank itself. In order to get the most volume they tend to add a few cm's to the tank depth along with increasing length and pushing in to areas of space not used by the factory tank. Frankly the sales pitch of volume is no substitute for the real argument of usable fuel. The main issue is tank depth, they cant (or wont mostly due to warranty and legal issues) increase the length of the power cables to the pump housing, that means they are stuck with the pump at pretty much the traditional position, manufacturers don't leave much wiggle on wiring looms these days. So if you look at the drawings below the factory setup sits in a perfect location to get almost all the fuel available.
In order to get the best use of the tank you need to drop the pump back to factory scavenge height off the bottom of the tank. It is possible with plastic to make an extension but the connection will fail over time. There is another way though, that's to make an alloy bracket to cradle the whole housing, you will loose a couple of mm in scavenge height but its a better way of securing the pump than plastic welding or a substitute section riveted to the existing housing.
Of course you could also just choose a tank that has usable volume with the factory tank depth, Ive been looking at the LRA tanks, has anybody got one of those installed yet?
http://www.longrangeautomotive.com.au/i ... xr_web.pdf