This stuff works great for hanging filters from the ceiling of the tent -
http://www.lowes.com/pd_302463-75332-WHITE___
The holes are about an inch apart, and 1/8 inches in diameter. You can cut the pieces to fit, loop it around your filter, and line up the sets of holes and screw 3/16 inch screws into the holes to hold the straps together. If you can't see it in your mind's eye, I'll post pictures tomorrow. Lights are out at the moment. Great stuff; flexible enough to work with, but very strong and doesn't seem to stretch at all.
To make the poles in your ceiling more rigid, I suggest measuring the inside diameter of the poles. If they're 5/8 inch poles, inside diameter should be about 1/2 inch. Go to Lowes or Home Depot and buy 2-foot long sections of 1/2 inch steel rod, and insert them into the hollow poles to stiffen them. I do this to every horizontal pole that bears weight, including the two horizontal poles on the side of the tent because they support the horizontal poles that support the light and fan. Don't buy rebar; it usually is too wide to fit. Buy smooth steel poles. They sell them for a few bucks apiece.
You don't have one of those tents that has the cheap plastic corner brackets, do you? Not to judge, but those are a disaster waiting to happen. I replaced mine with copper elbows from the plumbing department. Braced the top corners with "L"-shaped brackets secured to the poles with hose clamps, and that tent is staying upright, period. I never have to worry about bumping it or waking up to the crashing sound of a 30-pound light or filter smashing a pound and a half of White Rhino into pulp.