Those pipes will definitely float it. I would only have a real wide ramp ( 4ft just like one side) ducks love wide way more than the skinnies. Im betting your original design works as planned.
as always you must post pics of the completed job.
Just checking in on this thread. I have built the floating house and I'm about ready to send it on it's maiden voyage. Made one big change. Decided to float the house on one gallon jugs instead of PVC pipe. The pipe was just going to be WAY to expensive (1.5 times more than all the other materials combined) so the jugs will have to do. I have framed the bottom with 2x6's and the gallon jugs will fit perfectly inside the frame. Using somewhere around 72 gallon jugs so that calculates out to almost 600 lbs of buoyancy. More than enough. I will be posting pics of the launch. Wish me luck.