I missed the reply about the jib crane until now - I was a bit preoccupied with something when you posted it as you will soon find out in my build thread. Anyways, allow me to make a couple comments.
First of all, it looks very functional and I’m sure you will get a lot of use out of it.
I’m putting my engineer hat on now so God help us

. Using your numbers of a 84” beam, tension strap connecting to beam at 42” out and maybe running up at what appears to be a 45 degree angle, I calculate 282# of load in the tension strap for every 100# of load out at the end of the jib beam. I’m just guessing on the strap angle and I’m leery about that 42” number since it doesn’t appear to attach to the beam at the midpoint - it looks closer to the column in the pictures. That would push that 2.82:1 ratio even higher. And the tension strap looks bigger than 1/2 by 1/4 - maybe 1-1/2 x 1/4?
If trying to maximize the lift capacity, I would suggest adding a gusset were the tension bar welds to the top of the vertical column. If that bent strap straightens out under extreme loading, the beam will droop and it's all downhill from there (literally

).
The other thing I would consider is some type of limiter in the track when you are lifting something
really heavy and don’t need to roll it out all the way to the end. If the jib beam starts deflecting more than you expect, it could get away from you and roll uncontrollable downhill. I wouldn’t suggest using the standard Unistrut nuts since they bite into the channel right on the same surface the wheels roll on, but I'm sure you can come up with something easyto lock down when needed.
Since you have that nice digital scale, it would be interesting to see some numbers from a quick load/deflection test. Put a couple different load out on the beam at a known distance and measure the deflection at the end of the beam. It will help you predict deflections at any given load, if you are curious.
At the end of the day, only you really know what this thing is capable of and what you feel safe using it for. Use your best judgment and be safe
