Sorry I'm so late to the dance. Just came across your thread when I was searchin' out LED grows.
If you're still having light leakage issues try these:
https://hachol02.hafeleonline.com/OA...55DA179CDAD2C1
or something like them. They're called elbow catches and can be had in a variety of orientations. They give you a very positive latching on the less active side door. They also allow you to put a little pressure on the door when you close it, thereby more fully engaging and compressing your perimeter weather stripping. In addition to that you can install an T-astragal along the edge of the less active door panel. If that's not enough you can also try attaching another strip of felt or foam tape on the back side of the door so that it's right up close to the existing weatherstripping that I presume you have attached along the front edges of the cabinet carcass where the door covers. To do that you need to empty out the cabinet and alternately close each door and reach inside to properly position the extra tape. Kind'a ghetto but it creates a kind of weir for the light to negotiate and it can only bounce but so far. To further immobilize the more active door panel you can also drill a hole up from the bottom shelf overhang (assuming you have a recessed toe kick, and do the same down from the top. Stick an Allen wrench up or down in the hole as an added bolt that also isn't obvious to casual snoops.
I also seem to remember you having some questions about ventilation, maybe in your other post? Anyway, Yate Loon makes a 120mmx120mmx20mm 12 VDC computer fan that sells for about $4-5 and moves 45 CFM at just under 21 dBA and less than a third of an amp. You can get a stand alone 12 VDC power supply for $10-15 that will reliably power 4-6 of the fans if you don't have an old computer PSU to scavenge. The issue of stink control is best addressed with one of the DIY solutions IMO. Carbon is cheap and the name of the game is surface area. So a full width shelf sized tray of carbon could probably be hobbled together for just a few bucks (think retile cage lid with a dust proof fabric between the screen and carbon, and a WalMart furnace air filter underneath. Easy to renew, large area means easy breathing for your fans, and a larger available carbon capacity means better, longer performance between carbon changes. You can use the fans in a push pull or all pull, but generally the sleeve bearing fans perform better and longer in a horizontal install pulling air through the cabinet. Another good fan is by Cooler Master and comes in a 200mm (7.9") size. I caught them on sale for about $14 a while ago and they move 110 CFM at only 19 dBA (that's quieter than an average bedroom or hospital room at night). Depends on how much mounting space that you have. Try to work with the natural convective flow. That is to say, mount fans high for cooling since the warm air is trying to go that direction already. The quieter low velocity fans don't generate enough pressure to overcome the static conditions as well so trying to push or pull the warm air down to the floor is pretty much useless in a big box. The 200mm has an LED light in it but just don't hook that part of the wiring up if it's a problem.
Also with the duct work. I've forgotten the exact calculations (there's probably a free duct calc somewhere on the internet) but adding elbows kills air flow. Corrugated hose turbulence also kills flow. Straight shots of metal duct with taped (foil tape not that shitty "duct tape") are best. An interior plenum can be fashioned out of a Rubbermaid container, to use as the basis for your carbon filter as well as a fan noise and light baffle near your exhaust outlet.
Not trying to tell ya what to do, just noodlin' through a reasonable KISS approach. Let's say you steal some top space for a shelf sized carbon filter with the fans inside blowing out the top or the back near the top. Intake air from under or low and behind the cabinet could be drawn up through the floor in the front by cutting long slots with a router, or just cut a chunk out and replace it with a piece of egg crate light diffuser (Home Depot lighting aisle for about $10 a 2'x4' piece). If you use a router and leave a rabbeted edge on the opening that's as deep as the egg crate is thick, it will al sit flush when you put it back together.
You can use a piece of fabric or open cell foam on the outside of the egg crate as an intake filter by just painting a little glue across the face edges of the egg crate and sticking the foam to it. Make the free area of your intake at least twice the size of your combined fan diameters and shoot for about one complete air exchange in your cabinet every five minutes. Do the math and don't cheat 'cuz you only end up screwin' yourself. Two 4" fans don't equal a single 8".
Anyway, the air exchange is critical not just for temperature and humidity control, but also for your plants to perform photosynthesis and breath. As the convert carbon dioxide to oxygen they need to expel the O2 and get a fresh supply of CO2. With good ventilation, plenty of nutes/water at the right pH for uptake, the next limiting factor will be available light. Don't know what the inside of your cab looks like but it's pretty simple to add floros as you get the dough if you're so inclined. If you have room you can just add them to the walls for side lighting with your LED's. The CFL's are crazy cheap, and very effective, but you have to be a little more creative in how you mount them if you want to be able to move them around as the plants grow. Their ballast is built into their base so they also tend to throw more heat than a T-5 where you can remove the ballast and mount it outside the cabinet if heat is an issue.
Well, good luck. Hope I didn't just muddy the water for ya. Let me know how the LED's work out.