Join Date: Jun 2016
Location: Orange County, CA
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
I use Uniseals in each of my fresh water tanks where their gravity fill inlets enter in at the top. I suspect they wouldn't be 100% watertight if water sloshed vigorously around inside, but for what I've done with them I think they'll be fine. I wouldn't however put one in a black tank! The first time I pushed the pipe through one it dislodged from the tank and fell down inside, which was not fun to retrieve through the tank's 3/4" drain hole after the tank had been secured into position. I recommend using some sort of lube or glue to help the pipe slide through, and to smoothly chamfer the end of the pipe.
So saying, I hate cutting through anything structural unless I know for sure that there won't be any consequences from doing so. There's good reason that the body company put in those supports - if they didn't need to do so, would they have spent the extra money by including them?