Im buying brand name 250 watt rated dome fixtures, but the insulation on the wire gets brittle and falls off. I've never seen fiberglass sleeves on any of the wires in all the fixtures i've bought. That would make sense though. Can you point me in the direction of a dome lamp like that and or the wiring i would need with ceramic socket to put on the domes i have? they do have holes in them already for venting. I'm thinking the next thing if i cant wire up a new socket would be the wire cage fixtures but they look like they'd let out a ton of the heat i'm trying to capture.