More boat-towed-glider WIG questions

After searching the literature the closest thing to what we (my
brother and I) want to build is called the "Aqua-Glider" which is made
mostly out of wood. I thought we might copy the design but substitute
materials. For the fuselage and tail we would use fibreglass/foam
sandwich construction. Welded aircraft tubing for the tail section of
the fuselage (my brother has a TIG welder). Having a tubular after
body section (fuselage section behind the step) is a concern since
usually on takeoff that section is the last to touch the water and
also what one lands on, I've never seen a flying boat without one.

For the wing I was planning on using a built up wing with sheet
aluminium ribs with a wooded solid plywood or box spar. I was also
thinking about using an aluminium tube spar rather than a wood spar
but was unsure about how to connect it to the ribs? If one had a very
soft Al one might be able to form a circular flange that the tube spar
could slip into which could then be glued. Another way might be to
attach a piece of wood to the rib (both with holes though them) and
then glue the wood to the tube spar. Is their a better way to attach
Al ribs to an Al tube spar?

I know typically 2 or 3 layers of fibreglass are used for each side of
the fuselage with .5"/10mm foam sandwiched in-between. I couldn't find
a plan or information on using fibreglass sandwich construction for
the hull of a flying boat as most seem to use moulded fibreglass
construction or wood covered with fibreglass. Any ideas on the number
of layers required?

After reading a book about gliders and the high lift airfoils that the
Germans used in the 20s and 30s and since takeoff and flight speeds
are similar to the German gliders (around 25mph) I think I should
probably use a high lift airfoil. Although the NACA4412 airfoil and
thicker variations are very common on flying boats, I think most of
them used flaps especially with the thicker airfoils. I want to build
a simple wing without flaps. Since the following airfoils may be too
aggressive and are done at a bit too high a Reynolds number (2.5
million compared to 1 million): http://www.kaiyipboxing.com/WIG/INDEX.HTM,
does anyone have any suggestions on good airfoils to use or are some
of those okay to use?

I was also considering a Parasol type design for added stability. This
would allow the usage of a lower shoulder for the fuselage and rather
than mounting the engine in pusher configuration on the shoulder, the
engine could be mounted onto the wing. The problem with the parasol is
that I couldn't find any design for a parasol flying boat. I may have
to buy multiple plans and try to combine the two. Also since the wing
is so high, rather than tip floats I'll probably have to put
outriggers on the sides of fuselage. Does anyone know of any plans
that I could use/combine for this type of design?

Brock