Hi, looks like a good project. I prefer height of 6" above surface of calm water and maybe 8" when choppy. So maybe best if you could make the level adjustable to allow for conditions and weight of passenger and equipment. The wider and longer the boat, the more stable and the higher you can sit. Foam is illegal in some locations, unless well encased so I don't know what kind of coating you are planning. High density poly board is very strong and may not need metal reinforcement if thick enough, unless the plan is to use hinges to make it all more compact. Keeping weight down is crucial. One the first boats I made was a 4.5' version similar to your picture and it worked well. I used only 2 threaded rods to bolt the pontoons together and attached a canoe style seat in between to those rods- that kept weight and cost down. The upsides are durability, simplicity, low cost and stability if large enough.
The downsides are heavier than comparable inflatables, less portable, absorbs water if not totally sealed- results of less buoyancy and days to dry out, corrosion embedded in salt water use. The "flying brick" shape is very hard to push through water as goddess pointed out, elongated football shape with your butt out is the most energy efficient.
That's what my experience has taught me, hope some of this is useful. Hope you have fun building, as I did.
Pon
[quote sumo]Ok i am new to this type of fishing I am currently building a version of a float tube/pontoon boat and I have come to the point of determining how high i want to sit out of the water, I have never used a float tube before and would like some advice on how high to mount the seat , I know that the over all height will vary from person to person. I have noticed , by looking at the pics on this site that some tubes sit you below the water line some just at the water line and some out of the water all together, is their any advantages / di

vantages in each position or is this a personal preference . I have included a drawing to better show what i am working on.[/quote]
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