I have a 2006 Allegro Bay that developed a small leak. The only way I knew there was a leak was a rust stain that was coming out of a piece of horizontal trim just in front of the drivers door, just about floor level. Occasionally, the carpet just against the wall would get wet.
I went to Carpenters RV in Pensacola where they did the test. The only bubbles that showed up were about three feet directly above the stains at the top end of piece of the vertical trim. Lo and behold, the top end of that piece had no silicone. The vertical piece terminated at the widow trim. The water would channel around the window and flow right over the top of the trim.
For those that have a leak, this is a great test. Only cost $150.00.
I will go back every year or two just for piece of mind.
For those in the Pensacola area, I would highly suggest Carpenters RV.
First class operation with helpful employees.