Yes the long one would fit a computer and light as long as the light is not a bulky heavy one

I am using it to mount the front light on my aerobars. It works well and as long as you pad around the band it holds quite well.

I would say no, unless your lights are very lightweight. I believe that you would strip the threads tightening it enough to stop it swivelling under the bar with the weight of a light on top instead of a bike computer.

yes, provided the light is not too heavy, as it may move, however have not tried with lights but imagine it should be relatively stable provided it is tightened sufficiently.

Not sure why you would want a light on tri bars but yes i think it could

depends on the weight...

and the installation angle

Doesn't tighten enough to hold anything of weight in a horizontal but will act as a vertical post to mount a light underneath an aero bar.

Yes, I bought it for this reason and it works great. It is quite a bulky light and the weight of it does not push the mount down over bumps or anything. I would recommend it.

probably - depends on weight. But if you beef up the extension a bit with electrical tape, you should be able to tighten it enough to take some load...

could be done as long as the light was quite minimalist in weight,blackburn flea or the excellent knog frogs should fit a treat

I use this with a Garmin 305 with the quick release kit. I would have thought that the 310xt would be similar to connect. This is basically like having a small piece of handle bar - I would say that if you can fit the 310 to your handlebars, you should be able to fit it with this.

If you have the quick release/bike mounting kit for the Garmin 310 XT then yeah will work fine. I have used it with heavier Garmin computers like the Garmin Edge 500 & 305