Our trailer had a short vertical crack (maybe three inches long) in the shower wall just above the seat and in the corner when we bought the trailer about 3 years old - didn't notice t until a few weeks later!
I debated what to do about it.
In the end, I thought that if I tried to make it disappear, it might wind up looking worse than if I left it alone!
So I just stop-drilled the crack at the end and then filled the stop-drill hole with clear sealant
and ran a bead of the same sealant along the crack.
Eight years later it looks just the same - has not progressed any further,
Just in case you are not familiar with stop drilling, it is a common practice to stop existing cracks progressing further - you just drill a very small hole at the extreme tip of the progressing end of the crack. That relieves the stress and usually works to stop the crack going further.
If doing that, you really need to identify the very tip of the crack - I often use a very bright light and a magnifying glass!
If you don't drill the hole right at its very end, then the crack stands a good chance of going further.
If you do wind up veeing out cracks in the floor pan and trying to bond them, then it might look best after to repaint the entire shower pan with a suitable paint - I think that is what i would do,
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.