Yes. In the H3 technical forum, I posted a method on how to mount a fuel can carrier on an H3.
The step by step review link is here:
http://www.azhog.org/H3_Gas_Carrier/h3_can_carrier.htm
As for the back right corner - No, and it's not recommended for two reasons.
1) The cans will be closer in height to the bumper. It would be bad juju for anyone that places it there and gets rear ended. The design used in the review above places the can higher above the bumper line (higher than an H1 fuel can carrier, in fact.) There's pics showing the difference.
2) Any time you open the rear door, you have to swing the can carrier out of the way, which leads to #3
3) Where do you mount the locking mechanism on a right handed fuel can carrier? The spare tire gets in the way.
FYI - Steve