Insulating the hull questions.

[ebb]

Kent,
Injecting 2-part urethane foam between cabin and liner would be a problem because the pressure created by uncontrolled foam expansion will make your liner bulge like a pregnant dog. Don't believe the process chemicals have changed: reaction gasses are toxic, and because the cells are not truly closed cell the gases can continue to leach out... for (not knowing the stats...) for your forseeable future.
There are single part aerosol construction foams that advertise CONTROLLED EXPANSION - that might actually work. HOWEVER, you cannot prep the inside surfaces of the liner or cabin. Imco when they were made the last coat of polyester had wax added to get it to set hard. Foam that is not sticking in non-accessible places will hold moisture, get smelly & go bad. Don't inject urethane into your boat ! ! !
I believe just about any foam urethane is toxic, it never becomes inert.

Empty air space is a pretty good insulator.
Wonder how much condensation you notice on the cabin liner overhead when your boat is dew-pointing vapor ladened air and the windows are dripping. The top of the coach roof is balsa composite. Where the balsa stops must be before it makes the difficult transition at the corner curve to become plain fiberglass sides. The liner creates a hollow space which may also keep condensation from forming on the cabin sides in the cabin - but condesation may form inside in the damp space between the liner and the coach sides.

Impossible to seal cabin side windows (dead lights).
The strange original Pearson squeeze frame mounting system and floating lenses of the large windows use the bendy unfilled space between the LINER and the PLAIN 1/4" thick sides to make the ineffectual seal of the window frames possible at all. And as everybody knows, the windows are leak prone because of this poor design. It will be impossible to fill the vertical sides of the cabin with 2-part polyurethane foam, you'd have to create difficult jigs to keep the sides from blowing out the liner inside. There is no 'FLAT' to the existing liner. Even outside will billow out in places imco. In use polyurethane foam will disintegrate if it moves at all. There will also be voids & adhesion issues.
Actual partial filling in between liner and cabin sides with epoxy for alternate window systems has threads in this forum.
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The PVC/foam rubber product is a good candidate for that white paste. Very gluable. There are bigbox products available that will do better than regular contact cement. Better then water based contact cement alternative. What's likable about paste* is that you control thickness with the toothing of the applicator, means you can have less voids between the surfaces (that you will get using thin film high solvent contact cenent).
Have used the acrylic paste to fill seams around the foam cakes - making seamless embedded insulation. You don't have to do that, but no water will seep in and algeanate, no dirt, no little creature hotels. The thicker paste 'filler' eventually dries into a firm flexible rubber, and seems to be completely bonded with foam and various surrounding materials.

Haven't done it myself (we grinded down to green polyester) but if you dewax, clean, abrade and smooth the old painted surface, I'm sure the acrylic paste will stick - better than the old paint you are covering, most of which is bloody bonded to the hull.

Imco you can paint ensolite with flexible rubber urethane deck paint (without the anti-skid in it.) after it's installed.**
Haven't done it specifically. Prefer the smoother shielding surface of vinyl fabric. Which also gets totally bonded to the foam.

I have moral and chemical problems with PEEVEECEE. A UNIVERSALLY BAD PLASTIC. Think it is an unethical irresponsible plastic that in various forms is killing all creatures great and small on the planet. The ensolite I have is so old that its real danger may be its old age. My problem too. The vinyl I just got is low odor, maybe it passed its gasses into the MMC warehouse environment while waiting for my order.
Can't think of any any insulation products that are inert. Maybe balsa, the great insulator - but it rots. There are no CLOSED CELLS in nature...
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*Bostik makes a pleasant smelling, non-toxic, water based acrylic, smooth white paste for cork and carpet tile called InstantPro. The TDS makes it sound similar to the stuff i'm using. Remember I'm also using the 564 as an 'experimental' fillit - with a finger and extra paste radiusing the bottom of an ensolite panel where it butts the settee - to create a mopable waterdam of sorts.**
Open time (very important) discussed in the data sounds like my stuff. "Inside only" - may refer to constant water wet-softening the set glue. Might not use it in the cockpit! I'd worry about inside boat use if the closed cell foam allowed water in! Tend to trust Bostik products. (so far)
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**Have painted white water-based urethane rubber UltraTuff nonskid deckpaint (without granules) into lockers befor they become inaccessable to further painting.. Assume the stuff bonds to any exposed acrylic paste where ensolite was installed - sealing plywood and seams from standing moisture. Also rubber surface might add some traction for objects in the locker that hard stuff can't. Exposed to view, it's a lousey look, imco.