mike–nice job!! I decided to forgo the Li battery for now, and instead bought a 100Ahr AGM battery. my tongue weight is already 120 lb so decided to mount the battery under the floor, just aft of the axle, as friz did. I, too, fretted about drilling more holes in the floor (4 for the carriage bolts to suspend the battery, and 2 for the power leads) but I went ahead and used the drill-fill-drill technique for the holes. the holes and the heads of the bolts will be hidden by the mattress. most of our outings will be to state parks where there is power available, but if we end up off-grid more than I expect I might swap the AGM for Li so I can use nearly 100% of the capacity rather than 50%.
however, finding campgrounds with acceptable shower facilities (as determined by SWMBO) almost always include 30A power!