I've had a little experience with installing new construction tankless water heaters. Now I have a customer with a leaking water heater. He has a large upscale house with two 50 gallon propane water heaters and a recirculation system. The furthest distance to a shower is 65 ft. There are 3 existing baths with plans for a fourth. Also there are two kitchens. Normally it is just him and his wife but a couple times a year they have a very large number of guests and do serious corporate entertainment at this lake home. I need to know how to size this swap and any info or details related to the recirculation system. Any help is appreciated...