I don't know about Scamps, but from what I've seen Boler
used many different materials over the years for "door stuffing" in many arrangements. I would be a little surprised if Scamp was totally consistent, although I suppose there is more potential for that given that they only have one factory. Still, I wouldn't be sure until I actually saw the inside of a door (yes, I've seen too many boats that were "supposed" to have "x" material but had "y" instead
Here is one thing to keep in mind when you are re-coring your door:
The door has a curve, yet gravity makes it want to be straight. So you have to build in a way for it to keep a curve. Some people have done this with a frame, and that works, but.... you have the means right in front of you to do it with core. Since you have de-cored your door, that's probably what I would do in your shoes.
So you have three missions:
1) Get the curve right.
2) Repair the door so it will hold that curve.
3) Keep the inside of the door dry.
On #3, that is important whether or not your core materials can rot. Besides the obvious weight
and general "ugh factor" of a soaked door, the water can also lead to debonding (where the core and the skin separate) which will cause a failure. This holds true for non-rotting as well as (potentially) rotting core materials.
It's the same story in fiberglass boats, which almost all use a cored deck structure (and some now have a cored hull as well). In early days it was not all understood well, but even now that we know, many boats are still built without adequate water protection to the core, in my opinion.
Luckily, you are not trying to crank out 2,000 trailers to a price, with paid labor, so you can take the extra time and care to make yours right, without worrying about going over budget, angering the boss, etc.
So, for the sake of my post, let's say you are going with a new core and then a fiberglass skin (again) on the inside.
Let's assume your door had the right shape (fit in tight at the bottom), and if it doesn't you can post back and that can be a separate issue (that you would want to correct before proceeding).
So, you get the hideous old core out of your door (that "sweet" smell was probably a styrene/fiberglass smell). Here are more steps you will want to take. The order can vary slightly. Also, I am leaving out some small details to keep the post from being uber long.
1) Remove hardware and window
2) Clean and prep inner surface of outer skin (sand off core and rough up fiberglass surface; clean with acetone) (normally I would say denatured alcohol or acetone but since there might still be traces of mold contamination....)
3) Clean and prep flanges that remain of old inner skin (sand to give tooth and solvent wipe)
4) Decide whether you are going to try to re-use inner skin, or whether you are going to lay an entire new inner skin. Either can work
5) Decide on core material (balsa or foam are common choices) and have proper thickness on hand. Given the curve I would go for the scored material
6) Bend core backwards (like a cut mango) and fill scores with thickened epoxy
7) Bond core to inside of outer skin with epoxy. Fair until level
8) Now you might have waited until cure to go on. If so, wash off amine blush with water and a 3M scrubbie, then sand and wipe
9) Use epoxy to bond inner skin to core, and/or lay up new skin. If new skin, run it over your "flaps" on the old inner skin so that you have at least an inch or more of overlap. If you are using the old skin, match it up so edges are flush
10) If new skin was laid up, fair it and go to step 14
11) If old skin was used, you now need to sand/prep the area for about 2" outside the cut lines on both sides. If you dish them, you will end up with flush surface; otherwise it will stand proud
12) Now lay on "tabbing" over cut line (you can use fiberglass tape to avoid hairy edges, although you will get a slight ridge if you did not dish the sides)
13) Fair as desired
14) wash amine blush off of whole thing, light
sanding, wipe, then you can paint
Keep in mind that the bond between skin-core-skin is what keeps the door curved. It functions like an I-beam where the core serves to keep the skins separated, and that's what gives it the strength. Conversely, that's why a soggy door will sag; the skins have effectively de-bonded and there is no more "I beam."
Edit: Oops, I forgot to address #3, which is to keep future water out of the core.
I would do it like I do on boats, and, as a bonus, you will already have the materials to hand
Basically, although you do use caulk or other material (such as butyl tape) to "bed" the hardware, you don't want to completely rely on that to keep water out of the door's core. I like to "close out" the core. There are a couple of options:
1) After you core the door, "reef out" the core for a half inch or so around the hardware/window openings, and then fill those areas with thickened epoxy (for screw holes you can just drill a larger hole, fill the whole thing, and then re-drill your new, smaller hole).
2) Lay those areas up with solid glass/epoxy as you re-core the door.
Now, you still bed your hardware in order to keep the water out of the inside of the trailer, but when it fails (and it will, they all do in time) all that happens is you see a bit of water coming into the trailer and you know it's time to re-bed the window, the door handle, or what have you. What you *don't* have is water silently and evilly seeping into your door core.
A side bonus is that you also get a firm annulus so that when you fasten your hardware to the door, there is no tendency for it to suck the skins together, promoting leaks