Hi,
I only had 4+4oz deck / 4oz bottom glass jobs on my PU shortboards so far and was thinking about ordering a board with heavier glassing next time to increase the durability.
What do you reckon is the weight increase going from 4+4oz deck / 4oz bottom
glassing to 6+4oz deck / 6oz bottom on a 6’4" PU shortboard? 30%? 50%?
Thanks
Of course you did! I did reverse speak on your post and the word Epoxy was clearly legible. We know what your thinking Mr. Daniels. You and Jimmy Page.
I didn't mention epoxy, LOL.
The op asked what the weight increase would be if he went from 4/4/4 to 6/4/6, assuming the shaped blank stayed the same. What do you think the weight increase will be?
You're going to add at least 1/2 lb (200-300gr), probably more. In addition to the added fiber weight, it takes more resin to lam and hotcoat. You'll also stiffen the structure considerably.
Spoken like a true Epoxy loyalist. I have to disagree with the "1/2 lb. probably more" guestimate. It's all about Gruuby Clark's motto "High strength to weight ratio". You want lite weight you have to trade off a little strength. You want strength you gain a little weight. The simple truth has already been expounded on by surfding in his comparison posts on Marko, US blanks and Surfblanks. We're talkin' way less than a half pound. But I don't think another Epoxy vs. Poly bash is what Logan is after. I think he was more concerned with the differance between the two cloth schedules both in weight and strength.
I can't give you an exact weight increase in ounces, but can tell you that if you are used to a four ounce glass job you will notice the differance. Once you adjust to it it's not a bad thing and the durability is a plus. I said it before; If you walk into a So. Calif. glass shop with a finished shortboard blank and donot spec. your glassing schedule, you will most likely get a 6 oz. bottom and a 6&4 oz. deck. Sanded finish. The O-zee's can laugh if they will. That is a standard glass job in Calif. unless you specify otherwise. I recently had a couple of longboards done with a six bottom and a double six deck(not my usual). The weight differance was noticable. A second layer of six really soaks up the resin. Six and four on a longboard deck is my preferance.
It’s just a little bit of math I would say. Here are the numbers of my used epoxy and fiber taken from the producers homepage.Would say PU isn’t that much difference in weight. Sorry for the calculation in meters and gramm, can’t really handle your versions 
166 g soak 136 g resin. 105 g soak 86 g. So one squaremeter weighs 302 g in ca 6 oz glassing and 191 g in ca 4 oz glassing. It’s late and I’m not sure if i calculate right, but 302-191=111. 111/191=0,58. So its an increase of 58% for the last layer.
Well how much surface is on a shortboard? Would say a 6’0x19’’ that’s guessed 0,75 squaremeter, i would say for a narrow board even less.
For 0,75 squaremeter the weight of a 4 oz top layer is 143 g and if you use 6 oz it’s 226 g. So you add about 83 g of wight and that should be about 3 oz.
3 oz really sounds ridiculous… I would say you feel the increased stiffness and not the weight. Just don’t eat breakfast and you feel more difference in weight 
I hope I don’t blame myself with my amateurish calculation.
Use a higher density foam, and keep the 4x44. I had a fish with surfblanks RED foam and 6x66, bombproof, but hefty. NExt one was surfblanks RED again, but 4x44. Holding up very well. Surfblanks RED is one density up from "standard/everyday" shortboard foam, and 2 densities up from PRO/disposable foam. Maybe you could ask your shaper for a harder density?.
A 6x64 glass job won't save over shaped foam.
When you are ready to step out past the "standard shortboard" I can help you......McDing can help you too...
Most shortboarders would have no idea if I glassed their board with a 4 oz bottom or a 6 oz bottom.....When you learn to lam and hot coat and sand you will understand why my workshop is called the Low Tech Lab.
...A hand lam and a hand sand.....hot coat too...and a gloss coat...throw your math out the window......
6 bottom and 6/4 top...very strong...flex is another game......feel not numbers.....
Ray
Thanks everyone for all the replies.
I think i try 6+4 / 6 on my next board.
epoxy resin and a pe blank is a good combo also