The Waxoyl is the underseal!!!...After all this time, I didn't bother with cavities, I just Black Waxoyl'd the wheel arches, let it set, then blasted the whole underside with the Waxy stuff.Did you not have it undersealed before you did your work?
I'm in the process of getting mine booked in to have the cavity wax done. I'd previously bought all the Dinitrol gear to DIY the lot but the English weather has me reluctant to be crawling round in my overalls, therefore its time to pay a man.
I figure anything is better than nothing at this point, and there is, allegedly, some rust conversion properties, so if I do Dinitrol next summer, Hopefully it will be an improvement...