What type of hose clamps are you using. If using the flat metal band worm drive type get rid of them. Switch to the wire type, tower top or crimp styles.
Get a radiator pressure test cap and pressurize the system non-running and cold and see if leak down occurs. You can also much easier see where leak is at in this mode (if it leaks).
If it does not leak cold then inspect the metal where hose attaches for micro fine crack line.
