I had a look at long range tanks and they looked really expensive, like a couple of grand, if anyone knows a cheaper way to get one (made by someone perhaps) then I'm all ears :)
I have both a LR tank and rear bar, but only fill the jerry cans when I really need them and use them up as I go. The Long Range tank I picked up for a few hundred dollars from a guy wrecking his D1 around 5 years ago. If you are prepared to keep an eye out, they do still turn up, so you don't need to buy new. Same thing with the rear bar and jerry can holders. I also recently picked up a couple of 45L sill tanks that way too, which I probably won't get around to installing now and will more than likely end up selling.
For me the rear bar definitely is a compromise weight-wise but mainly to keep the CoG lower (hence why the sill tanks are a great idea). It also means the Jerry cans don't take up space on the roof or in the cab - D1's can be tight for space when touring anyway. When I am in full touring mode (ie. heavy & with a roof top tent), I drive pretty conservatively and inflate my rear helper airbags a little to level out the rear. The jerry cans in the rear bar can come in handy though, especially when it is New Years day and you forgot to fill up the night before, and all the servo's in towns North of Tennant Creek seem to be closed till later in the day! [bigwhistle]
The mount onto the door itself is substantial... however, I have had to weld 2 of the three studs back on (previous owner loved tightening things real tight!!) they pulled through plate, a few spot welds on the remaining good one now prevents it from ever occurring again. The stud connections are the weakest link in the chain, weld them in from the rear to give you total peace of mind. you will need to remove the mount to this obviously