Buying a trailer .Help!!

I managed to break the weld between the spine and upright on a kayak trailor with four boats on. "get us home" was use my built like a proverbial sea boat as a rest for the other boats. Cure was triangulation between spine and upright. Axle position needed modifying after initial use. Moved it back 18 in. to get stability.
 
im just looking forward to get a trailer that's stable and easy to get the boat on.
my current trailer doesn't self centre the boat and it ends up tilted
 
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