Hey Waterman, I have a 94 V21 and have no issues with stringers or transom at this time. Having said that my brother in law looked at 3 or so V21's while he was in the market for a boat. All of them had soft spots in the floor. Mainly between the transom and the rear round inspection hatch. Check around the hatches really good for sponginess.
Another thing I don't know about all V21's but the forward rod holders drain down into the foam under the gunnels. I want to apply hoses and route them to the bilge just for rainwater and washdown etc. but in the meantime I take special care to make sure water doesn't get in the rod holders.
I haven't heard of any transom issues with V21's, not to say there aren't any.
Good luck they are great boats.