Water Tank Beam

I posted about this topic  back in March 2014 shortly after I took delivery of my Rpod 178.

Personally I avoid drilling holes into frames, as they do reduce the strength.  Is it significant?  I don't know, depends on how much the frame is over engineered.
A single hole on one side reduces the strength less than a through hole in the same spot on both sides.  Of course the smaller the hole the better.

However- sometimes there is just no practical way to get around it.

Nightmare scenario!  Looked under my 181 this morning and saw the same thing.  I wasn't too worried about the black or gray tanks, they are always empty when I pull out from anywhere, camping or home.  But I didn't like traveling with even 10 gallons in the fresh tank with out a better attachment.  This morning I drilled through the frame and installed a 2 3/4" X 5/16" bolt and ny-lock nut in the 2 empty holes.  I feel more secure now.

Thanks for this post.  I checked under my 179 and found the same thing for all three tanks. Each tank had two beams with one beam being welded in place and the other bolted in place so it can be removed to replace/remove the tank.  Although each bracket had three holes drilled only two sheet metal screws were used on each to attach it to the trailer frame.  My biggest concern was on one end of the black tank were there was a noticeable gap between the bracket and the trailer frame (~1/4"). This would make it even more likely for these bolts to shear or pull out.  I ended up adding a third 1/4" diameter screw to all except one end of the fresh water tank where I could not get access.

Tank support seems to be an industry problem since the manufacturers like to squeeze every last penny of profit out.
Back in 99 or so my Tahoe toy hauler severely bent the thin sheet metal angle supports holding the 4 tanks*.  I replaced them all with actual angle iron that was much stouter.  Went from something like 1.5" angle that was 1/16 thick to 2" angle 3/16 thick.  Problem solved.

*Yep 4 tanks, one grey, one black, and two ea 50 gallon fresh water tanks.   Toy Haulers back then were not seen much outside the dirt bike/ATV world in the deserts out west.