Jeff, sEs, Bob, Herb, et al,
Thanks so much for your input. You have eagle eyes -- and this forum is proving to be worth its weight in gold. I'm not an engineer and not even very mechanical, so you offered exactly what I needed.
I have no idea why I assembled the frame box wrong -- but I sure did. I was probably obsessing over getting it square, and when I finally got it square -- I quickly cranked the nuts down tight and forgot that they also had to be located in the right place. Will correct that right away.
I am aware that by going with encapsulated tail lights, I gave up the license plate light. I plan to mount a bicycle light with a battery next to it -- properly aimed and shielded. I also don't plan to use the trailer at night, at least for a year or so. But I suppose it is still illegal not to have the light there.
The extra support for the tongue below the frame gave me more pause for reflection. I hate mechanical work -- so I thought long and hard about it before doing what is probably a pretty simple fix.
I would check with Trailex about making these changes and show them the pictures. IMO, I would have two more pairs of brackets (front and back) for added support from the box frame to the tongue of the trailer.
I grew up in the school of "If it's too strong, you'll never know it."
In the pictures the length of your box frame looks short. Was this changed for some reason or is this the way it's supposed to be?
I share sEs's concern.
Originally, all the weight of your boat was being carried by the tongue resting on the suspension box. As you have modified it, all the weight is now being hung from 4 T-Bolts. I read somewhere that some people have had problems with the T-Bolts fatiguing the area in the channel that they fasten into causing cracking. With sEs's suggestion of two more brackets, you would have the weight carried by 8 bolts.
I pondered that a long time -- first to understand exactly what the difference was between the same brackets holding the tongue above the frame box vs holding it below. And second, to figure out if I agreed. Well, you both convinced me. In the tongue above position the weight of the boat & cradle cross bars is laying on the frame with the brackets only serving to hold it in position. In the tongue below position the weight is hanging on the brackets and thus on the bolts.
OK, but is that a problem? The boat and stowed gear and crossbars weigh, at most about 300 lbs (probably more like 200 for me most of the time). Three hundred divided by the 4 bolts is 75 lbs per bolt. Even if a weight were simply hanging from the bolt and bouncing up and down that would be -- what -- a few hundred pounds? I'm guessing that a 9/16 bolt is way more than up to the task.
But the weight is not really hanging from the bolt. The bolt's purpose is to squeeze the bracket against the frame. The weight of the boat is held by friction between the frame and the bracket. Actually, that is probably the case in either the tongue above or tongue below position. In the tongue above position, the holes in the bracket probably hold the tongue a small distance above the frame. TrailX would have had to spend a lot on precision machining to actually let the tongue rest on the frame.
So the the question in my mind is, Can a 9/16 bolt with the 35 ft-lbs of torque TrailX calls for, hold enough friction (would that be called torque? Don't know) so that 75 bouncing lbs would not slip? Again, I'm guessing that the bolt is up to way more than that. Herb, you suggest that the frame may not up to that amount of torque. But I've got to think that TrailX had that in mind in their original design.
Anyway, sEs won me over with that great comment, "If it's too strong, you'll never know it." That's my general approach to car top carrying, wrapping packages, etc -- which drives my wife nuts. So I called TrailX yesterday to order 4 extra brackets.
Ken answered the phone. He did not see that there was any difference between the tongue above the frame or the tongue below the frame -- even when I said that the tongue originally rested on the frame and now it hangs from 4 bolts. He also said that other customers have also moved the tongue below the frame without adding any additional brackets, and that they did not have any problems. So I canceled the order and went sailing for the first time in my life! What an incredible experience. I'm hooked!
By the way, I can now float the boat well up onto the trailer, rather than having to wade further out and lifting it up. Thanks again to all for helping me to think through this and work through it.