What is your concern, exactly? Too much weight causing the tent to collapse?
As others have said, tents are usually built with plenty of strength to support what you plan on hanging from the top.
BUT... if your deadset on giving more support, you could use a 1/4in (could use 1/2 in, but thats adding even more weight, and likely isnt necessary for what im suggesting) sheet of plywood on the underside (the side of the bars facing your plants) of your top cross bars to more evenly distribute the weight of your equipment.
You could use some of pipe brackets (Like
THESE) to attach the plywood to the cross bars at various locations. Then you would just need to figure out how you want to mount your equipment to the plywood. But plywood, with plenty of mounting brackets spread evenly, should redistribute the weight in your tent, affording you a lot more stability, cheaply.
The only way to do this though, will be to remove the cover from the tent.. you'll need to have access from the top and bottom of the bars, in order to install the plywood. And id use nuts/bolts with large washers to attach the plywood to the mounting brackets, as opposed to screws... the washers will also help with weight distribution at the mounting points, and while screws COULD do the job, you wont have to worry about a nut/bolt combo pulling loose like you would a screw.
You could also get PVC pipe (probably only need 1/2in-1n pipe), and cut it so your upright corner bars run inside of the PVC. This will give support to the uprights themselves, and because of the wider diameter, when they press against the plywood, theyll provide more stability and redistribute the weight better. Not sure if this would be possible though, as the PVC itself is likely 1/8 thick from exterior to interior of the walls of the pipe. So your adding roughly 1/4in front to back, and left to right on the exterior dimension of the uprights, which MAY be too much, considering how tight the cover of the tent usually is when trying to fit it over the frame
Drew this up on MS Paint just to kind of show what i mean, in case its hard to visualize what i mean as far as mounting the plywood, and the uprights being inside of PVC cut to length
