While there aren't a huge number of aluminum trailers where I'm located, there are thousands of boats of that size with offshore brackets, pods, or whatever you wish to call them in your region. Supporting the bracket is taken into account in the design, it's not an issue. I also work with boat builders that use brackets and they have no problem designing a transom for that purpose.
I'm not that concerned about the reason Bob posted the question, it was the question that was being answered.
After doing a quick search on aluminum trailers I came up with many pics of this style of construction, some even showed the bunks to be aluminum tubing, similar to what the trailer frame would be made from, so strength and support doesn't appear to be an issue. Others used some very large wood beams, these aren't 2X4's. This method of construction actually gives a little more ground clearance than if the frame extended all the way back.
Now for the balance, If the tongue weight is correct, and I have no reason to assume it's not after looking at the number of boats on this type of trailer, then what's the problem? If the balance is correct the motor and axles will be located the same distance apart whether the trailer extends further back or not, it just looks more radical with a short trailer frame.
So far no one has come up with an actual reason why it's a problem, only some speculation based on how they feel it looks.
