My SBS trailer has two big rings at the stern on either side, standard fit, so a ratchet strap from one of those, up through the transom towing eyes and back down to the other one, and at the bow end, the winch rope (I threw away the stupid polyester strap that comes with the winch as it started to fray after about 10 uses and I fitted 6mm Dyneema winch line which is much better and at 3200kg breaking strain is also a lot stronger).
There is then a second 10mm nylon rope with a carabiner which clips onto the bow eye then the rope takes 3-4 turns up and down from the eye to the the main trailer frame (not the winch post) and is then tied off to the frame.
The hand winch ratchets are crap and should not be relied upon, but I wouldn't strap over the tubes if I could avoid it. A second rope to the main trailer frame takes minutes to fit and unless the bow eye comes out is unlikely to let the boat start planing on concrete