How do I install horizontal propane tanks in my Lance 1161?

Short term solution:

I took my two 12 year old 30# propane bottles to AmeriGas to be recertified.

The recertification cost $10 each plus parts if a new valve is needed. My bottles didn't need any parts.

I was told that all 660 AmeriGas locations can do it.

I could have ordered new 30# propane bottles for about $45 or so each from AmeriGas (they don't normally stock 30# bottles)

I was also advised to not mount propane tanks on the rear of the camper.... a potential liability issue. DOT wouldn't like it either.