This would be a good solution for you.
DIY Aquarium Screen Top Netting Kits - Bulk Reef Supply
As for clowns jumping? It is very rare. I had a pair of b/w clowns and while I was at work, started having some stray voltage issues from the heater I had in the tank at the time. Found the male behind the tank when I got home. Needless to say, I have a new heater and I actually had a small clown remaining in my 36 bowfront that needed rehoused... sad to see a fish I liked go, but I do really like the orange and b/w combo now.
In terms of 'blocking' light...there is probably some light restriction but isn't a problem. If it was, I think at peak I only run the radions at 75% power so there is lots of room to go up. LEDs pack quite alot of power, especially when it comes to penetrating water. Much more efficient that lighting that requires bulbs.