The dealer I bought my Argo from recommended using medium weight chainsaw chain bar oil for the chains; dispensed through a squeeze ketchup bottle. That is how he maintains all of his customers machines.
Whats the advantage of using PJ1 as chain lube?
Insofar as weight restrictions for the rear of the machine, I always assume they mean with a full tank of gas, low air pressure in tyres, bad weather conditions etc. In effect, they are only so restrictive to cover Argo's ass from potential lawsuits. The 6x6's can clearly carry more weight on water if the weight is well balanced and the weather is calm.
I am going the electric way for motoring on water. I am not interested in covering large distances with a loud outboard; just looking at a way to get around on water without making so much noise. The Loons and the Blue Herons on the pond let me drift within 30 feet of them, but as soon as the engine fires up they back off. The birds don't like the roar the Briggs so much, the fish are likely the same.