Good questions. Hope these answers can help.
Yes, if there is water intrusion your substrate could be affected. Fortunately, if this were to happen your aluminum structure will not be affected in the same way as a wood structure which is one of the major advantages to aluminum and ETERNABOND. The other main advantage to aluminum is the weight savings.
The roof is EPDM rubber with a 12 year warranty. It is laid on 3/8" decking that is fully capable of allowing you to walk on it for service and maintenance. The rafters are 5" truss-style on 16" centers. Crusader has R-14 fiberglass insulation.
Crusader uses a laminated floor and sidewall structure that derives its strength from the bonding process. The stud location can vary depending on each floorplan. The doors, windows, and various cut-outs are framed in aluminum for structural integrity when installing the component.
Aluminum holds up extremely well during cold weather but it can conduct moisture just like your door frames, window frames, glass windows, and even wood studs. EVERY RV is vulnerable to condensation in colder temperatures if not properly ventilated.
Although, I'm not exactly certain what you're weighing the ETERNABOND features against, I will also say that a major benefit to ETERNABOND is that the solid foam insulation will never "settle" in your sidewall over time ensuring a much better insulated fifth wheel. The laminated structure will also be quieter.
If you'd like to talk with a sales person or send us email inquiries, please feel free to do so at Prime Time Manufacturing, Manufacturers of travel trailers and fifth wheels
Best of luck with your research.