bottom of my formula board was totaly fked .. around the fin and nose thier is still crack in the foam y can see .. suprised bout the **** quality of foam used inside it .. plan is to smother in resin and wak the skin back on with a heap on weight on top .. .. .. .. .. .. yerp
good luck hope it doesnt snap at the cross joins, there is still delam under the fin
anny thing will be an improvement on what it was .. fel like i was rideing a inflateable board
lol
nicko's dads garage was my grandads garage for 35 yrs of my life 
He kept it spotless (he vacuumed the floor twice a week)
But he would love the fact that something was getting ripped apart and re engineered
Thanks Nicko you have made my week mate
Eric - wish you were still around - miss ya grandad
get out the spray foam, wack a layer down, sand the shape you want back.
layup and bag on a 3mm pvc sandwich then bag on some glass on the top.
then watch as the next time it get hot it delams again, right before you eyes 
That sucks, but that is the way lots of these big lightweight boards are made these days, windsurfer, kite race boards and sups.
You would be better off adding some light weight filler to the epoxy resin to bulk it up a bit so you increase the glued surface area.
Or another option might be better to take to a surfboard guy who makes epoxy boards and just have him layup straight over that big hole you got 
Polystyrene is just polystyrene, lightweight balls lightly stuck to each other.
a Quote below from the boardlady
boardlady.com/maintenance.htm
"Always leave the bag open, until the board is totally dry!
And for you windsurfers who listen to my preaching about opening the vent plug when not on the water: if you open the plug, then stick the wet board into a bag and zip it shut, the moisture from padz and straps will find its way into the EPS foam core. Don't go there!
And speaking of vent plugs: opening yours whenever you are off the water is the single most effective thing you can do to prolong the life of your board. Leaving it closed will cause the EPS foam core to expand and contract at least once a day. You take any substance, no matter how stout, and you push and pull it continually, at least 365 times a year, and it will fail. Guaranteed!
It's not that much, you say? I just measured my Trusty Old 9'-4": typical summer day, near sea level, early morning, cool 60 degrees, it was 4 15/16" thick. Then the day warmed to 89 degrees, a thermal low developed, and the board expanded to 5 3/16". That is a whopping 1/4" change, or 5%!!
Get into a routine, where you tighten the vent screw just before you put on your harness, or some such thing, and it will become second nature, and you will not forget. But DO IT!"
Look at the size of the area where the divinycell has not adhered to the styro.
Why do we (as a group) put up with this mass produced asian crap?
Windsurfers need to start making warranty claims - as even after warranty is finished they have to pay up if it did not last as long as "reasonably expected". THEN maybe they may start implementing some quality control measures........
Hmmm,.. it actually looks like it adhered pretty well.
You can see that on the delaminted skin, the foam is still stuck to the skin and it's the foam that has been pulled apart.
Although there is a small section in the middle which is pretty clean. Maybe it started off there and extended out. 
Its not Asian !!
after closure inspection of the skin i have lifted off it has a few crack in the inside skin .... bad news for the rest of the board .. i can flex the hole board one hand on the fin and one on the rails i can see the foam is broken up down each rail and the 3 blocks of faom that run tail to nose arnt glued together anny more ..... i cant decide wether to just wack a tone of bog onto the board and lay fresh glass over top,probs hevier and more time consuming .. or use very small amount of bog and lay original skin back down,the finish will be nicer nothaveing to paint the hole bottom but i cany see myself matching the level right .. either way i wont have the patience or skill to do a good job ..
.. this is turning into a **** of a job .. oh man :)
If you can get the bottom to sit where it needs to, you can glue it down using small holes and syringes full of pour foam. Only little bits at a time though.
It will take a lot of holes and even more patience.
If you do it, you have to do it in small amounts to make sure you don't cause the area to expand with too much foam.
I used this to stick down a delaminated bottom on a wave board, and only stuffed up one part where I used too much foam. I think the trick was to have a lot of holes and inject the foam until it comes out of the other holes.
Of course you would then have to fill these holes after you are done...
atm im mixing up a think bog paste and makeing litle pads around the edge of the hole cut out .. so i can let it go off and push the skin dwn hard onto them once its go time .. the foam that stuck to the skin sorta fit back into the board ok it seams, so was think just a slighty thickend paste spread over the entire area would get it back to the original shape ..kinda,sorta i hope .. just gotta make that dam fiberglassing shop in town that doesnt seam to have set closeing times
