That's said, what are others experiences with saving weight on this build? Most notably whether glassing as specified is critical. 

You will save the most weight on any buils by being very careful with your epoxy usage.

My mates build hollow surfboards without any internal epoxy at all. They use expanding polyurethane glue for joining skins to internal frame. Personally, i'll use epoxy on my upcoming Kaholo project. Howver, I will be;

chamfering sheer clamp, keeping fillets real small, remove any pooling epoxy, using 3oz glass as it only needs a light fill coat, no cloth patterns, thinner material for transom. 

Cheers

Glass on underside (inside) of deck - My instructions said glass the entire inside surface, but where do you stand? I did glass from a inch or so aft of the deck stringers to an inch or so forward of them. As Craig Robinson said: keep the fillets small. I used one thin coat of epoxy inside.

Next one I'm going 3 oz cloth, or maybe I'll tape the inside seam with a narrow (1") strip of 3 oz and go no cloth, just epoxy outside. 

CLC has changed the design of the frames and structures on the Kaholo.  The original frames were 6mm and spaced 24 inches with bottom stringers and, I believe the new structural design has the  4mm frames spaces at 12 inches without bottom stringers.   Does anyone know which is the lighter build and how much lighter with epoxy, glass thickness...being the same?  Also, does anyone know why the framing and structures were changed?

I agree with Craig, save epoxy.  Fabric soaks up a lot and tends to float.  Leave frabric out or pull it hard when you spread the epoxy and retrim the edges.  Pull the resin hard out of all the cloth layup, then sand (lightly to clean up) and thin recoat...and sand again.  clean up all spills.  A multitool works well inside the hull on puddles, fillets and errors.  A speed file works best for broad surfaces.  Sand, sand, sand - sand the frames to fit, sand the frames to fit the deck, sand the glass, etc.  Start with speed file and go on to just your hand and paper.

check out my notes from phase 1, posted Oct 15

One thng else, I have noted that since the weather is colder, the bottom is showing frames.  I think the air inside has decreased in volume with temperature.  I am reheating, sanding and then will drill hole.

SupShelby = Yes - Kaholo needs a vent tube.

Catalina Charlie = the new frames aree full depth to bottom and I belieive this to be an improvement since it was tough to keep the bottom flat with two floating stringers.

Hokey hydro - Your right.  FYI I think a neat alternative to the stopper and tube in the kit is a compressor drain valve. Three bucks at HD, all brass, not the butterfly handle type.  I have a pic if interested.

Do the inner structure out of 1'' styrofoam....