Nothing wrong with it. Our twelve foot Grumman originally came on a Shorelander trailer, for a sixteen footer. 5 1/2 feet of tongue, between the hitch and the winch sure helped on a shallow ramp once. We sold that trailer, cause we had another one at the time, and would save money in the long run. Soon, we are going to build a new trailer for it (I don't like the one we have for it) but use all the same wheels, axles, springs, and everything, from the one we have, so all we have to get is the steel (most of which we have in our stock already), so it will be rather cheap. Also, we are getting a longer tongue on it.
With many of the jon trailers, the tongue is the only difference in length, and the winch post moves fore and aft. Plus, on shallow ramps, the length helps. Get the longer trailer. Also, don't get anything smaller than 12 inch tires. Sure, 8 inch ones are rated for it, but they spin a lot faster, which leads to faster bearing failure. Also, make sure the trailer has bearing buddies. There is absolutely NO reason for a boat trailer, not to have them. Best 20 bucks you will spend on your trailer.