Afternoon all
Can anyone point me in the direction or know where I may get hold of a small amount of strechlon bagging material ?
I have a job coming up that I don't do very often but do use the film , and I have run out 🙄

Cheers tony

Few issues stand out to me there, the Strechlon being one of them. However, there's sort of a perfect storm of not entirely suitable materials going on that is likely the bigger issue. 

For one, 600cps resin is not ideal. That is a hand laminating viscosity resin, which is thin enough to potentially work ok with infusion - but the other materials will expand on that issue as well.

4x8 is just about too big an area to successfully infuse with a 600cps resin. It is probably doable, but it is very much on the max of what I would attempt - especially when using biaxial reinforcement, and Divinycell. Is the Divinycell drilled and scored for infusion, or just standard foam core? If it is just standard, this won't work. You need perforations roughly every 2" to let the resin flow through to the surface. Then, biaxials are naturally a bit tougher to infuse. They compact very tightly together, not providing many channels of flow for resin. They can be infused fine, if your resin is low enough viscosity to penetrate. 2 layers is not a big issue, you would probably get good wet out with the 600cps resin if your area was smaller and the core was suitable for infusion.

Strechlon is also not really suitable for infusion. On flat sheets, this is mainly due to the effect Rich mentioned earlier where the Strechlon can actually stretch into and seal off the flow channels created by the flow media, exasperating your flow issues. 

As for your sealing issues, the Strechlon wont be helping here either. Not only is it quite prone to porosity and punctures, but it doesn't stick well to the sealant tape, so you may well have a perfect bag that is still leaking through the perimeter between the bag and the tape. Your sealant tape may also be an issue - I suspect that if it isn't genuine Airtech AT200Y, then it will be an equivalent to. This stuff is not great, as it is quite firm and relatively low tack, which again exasperates the issues of sealing to the bagging film or even the tool. 

My first two suggestions to try would be a regular bagging film rather than a high elongation film, as well as a proper infusion resin. And if your core isn't infusion ready, either perforate it yourself or buy it drilled and scored. Those would be the primary suspects. After that, I would try a different sealant tape too. Your stuff will likely work ok, but it is much less forgiving, which can cause these situations where you tear your hair out looking for a leak that just won't present itself.

Tearing my hair out looking for a leak is exactly where I've been at for awhile now...
Your advice on using an infusion specific resin is spot on, but I'm going to jump on all the other details of your advice first in the hopes that if I get everything else right I can make use of the 30+ gallons of resin I already have and delay more hazmat shipping orders if at all possible.
(I have been degassing the epoxy in unmixed state and then metering out with a Michael Engineering Super E epoxy mixer with a static mixer as needed to the resin feed line bucket, so as to avoid excess exotherm or introduction of bubbles during the mixing process).
I perforated all the divinycell (by hand using finishing nails hammered into a piece of wood that I predrilled with narrower drill bit on a grid pattern, since I hadn't realized I was going to need perforated core at the time I bought it/availability in Hawai'i... I would be concerned with the holes becoming too small under vacuum since nails were pushed through vs drilling/cutting perforations except that my bottom skin has barely any, if any, dry spots but the top still has some dry spots even on my best attempts so far..).
What I've been infusing is actually quadaxial basalt as opposed to biaxial (weight 680 grams/sq. meter ie 19.9 oz./sq. yard with fiber orientation 0 degrees, 90 degrees, +45 degrees, -45 degrees and made with 13 micron roving), I'll try to get a good picture this evening in terms of the dry spots. Everything I've been making to date has been generally salvageable for non-critical applications a cabinet in a boat before I get things dialed in enough to do transom extensions and interior bulkheads but I'm running out of functional practice pieces so your advice comes at exactly the right time :-)
I can't say enough how much you've given me renewed hope dealing with resin infusions... :-)
David