My x17z came stock with one 30 lb tank, and yes, the bolts on the bottom are hard to deal with. (I used to lower the spare tire for easier access.) I was close to doing what Wayne did because it seems it would be an effctive solution.
I ended up mounting two 20’s instead. The kit is cheap and easy to install. Keep in mind if you do this, you will add about 20 lbs of tongue weight, but you will only gain 2.4 gallons of propane. To me it was worth it because I like to remove one tank once we are on site for use with a grill and/or stove. The top mounted fastener makes that much easier. If you alteady have two 20 lb tanks, the extra weight is not a consideration.
The real benefit is no more "talking" to the two mounting bolts.