[A/S] leak prevention in argosy

[f breed <temp4ident@xxxxxxxxx>]

hello all,
  our 1976 argosy 28' is an on-going project. we have noticed moisture under 
the rear bedroom cabinet, between the twin beds, against the rear wall. usually 
after a heavy rain. i have not been able to see the source of the moisture. i 
have inspected and re-inspected the trailer. i have caulked along the outside 
where the hose storage box and the body meet. up top, i see cracked paint 
around the vent but no sign that water could be getting through and if it did i 
think it would come thru the ceiling. what about the seam between the steel end 
cap and the aluminum roof panel? there is a little rust there and no caulking 
at all, should there be some there?  the forward steel panel looks about the 
same.  around the running lights also worries me. i plan to paint around them. 
i have reviewed all the archives on that topic. i did not see much about the 
metal prep. 
   another question is storage, i live on the canadian border in vermont and 
because of the slight leak i have been reviewing storage options. does anybody 
use one of those big rv storage tents? thanks for your input, jeff.