I don't think I have ever seen tie down eyes on the transom of any trailer sailor, but if I were going a long distance I might consider running a long strap from the trailer, up and over the cockpit. Also, when the previous owner helped me to bring my Catalina 27 to its current location (about a 100 mile trip that he made with the boat each year), he tied down the bow and the stern, similarly.
Having said that, I was once at a boatyard and the manager pointed out a MacGregor26 on a trailer with a strap exactly as I described, but with horizontal cracks in the hull right at the straps. He said, "That's what you get with a McGregor", explaining that it didn't have enough strength in the hull to withstand very much pressure. He didn't say the owner should not have strapped it, but rather he thought it was a combination of being too tight, given the lightweight nature of the fiberglass and the bouncing a trailer might encounter enroute.