Where to start?

As a garage project I want to convert an older VW convertible Bug to be amphibious. Can anyone here calculate if I remove the existing fenders, then build aluminum pontoons that hinge at the bottom pan and fold down around the tires when on the boat ramp, if it is possible to create enough buoyancy so that the water line remains below the bottom pan? I can also add a pontoon to the front to cut thru the water, pontoons between the front and rear tires along the sides, but the kicker is the rear. I cannot add too much flotation sticking out the back because the VW will have to be able to navigate the boat ramps for ingress and exits. using the existing engine and tires. For locomotion thru the water a simple dual bracket welded to the steering idler's with two electric trolling motors will allow steering to be controlled by the steering wheel, with battery power in the front trunk. The entire under side will be sealed and I will box in the engine/transaxle. The VW weighs 1980 pounds, the square footage is 60 inches wide by 180 inches long. I can install a 12 inch lift kit for more underside room for added flotation thicknesses. Most of the weight is in the rear half. As this is all new to me any pointers is welcome.

 

The rear of a VW would probably be one of the places you would want the most floatation, considering that's where the engine is. That makes it difficult.

 

I suggest weight distribution will get closer to front/rear equal, once you start placing batteries to power two large front-mounted trolling motors. You will need large ones, as the pontoons are going to add a fair amount of drag, and the bug body will have a fairly large amount of wind resistance, as well.
Without doing any math, I would bet that four deep-cycle batts, up front, will just about give you a 50/50 bias.

Roger