Here is another issue to consider -- the strength of the fiberglass cap that will support the ladder. I love Fun Finders, but the underlayment for the fiberglass tends to be thin (in order to save on weight, I guess).
On my trailer, the spare tire is mounted on the back wall. When I was checking the tire pressure on the spare, I noticed that it was wiggling. I checked the mounting bolts and discovered that they had dislodged the fiberglass on the rear wall. The whole setup was not strong enough.
So instead of using washers on the mounting bolts, I used a wide aluminum backer or plate in order to redistribute the load. Problem solved, and no harm done.
But if you were to screw lag bolts into similarly-thin fiberglass for an after-market ladder, I would worry about the strength of the fiberglass, since the manufacturer probably did not install extra beefy glass in anticipation of a ladder up front.
Maybe I am worrying about nothing, but that would be my concern, based on my experience with the spare tire.
2012 Fun Finder X-139 "Boondock Style" (axle-flipped and extra insulation)
2013 Toyota Tacoma Off-Road (semi-beefy tires and components)