any suggestions for securing the underneath storage bins? is there an affordable way to change the locks? i was told that the key to the locks are universal for all rvs... any advice would be appreciated.
Depends on the unit. I think most trailers are keyed alike (at least the key from my cheapo Terry opened the storage of a fancy used 5ver I was looking at). My motorhome factory claims they use 10 different keys 'at random' for theirs, but this may or may not be the practice with all motorhome manufacturers.
Check with a locksmith (who will work on a RV). We have only one in the Tucson area who advertises they will work on a RV. Or if the locks are those simple 'desk drawer' types (a cylinder with a bent bracket on the end), you might be able to buy a batch of them and do it yourself fairly cheaply.
Or you could add additional latching. One option would be to use those 'magnetic' latches they sell for childproofing cabinets. Takes a magnet placed at the correct location to unlatch it, so keeping the existance of this method secret would be your primary security. Or really get secure and mount an electric latch in each bay, powered from a switch inside the unit or a good key switch or keypad.
Manufacturers pretty much buy the same lock for compartments. However you can go to your local parts house and buy a full set of locks with matching keys that aren't CH751's or 7858's. which are the two most common.