Default [Q] 4.3 Custom ROMs will not boot

I just got a N7. It came with stock 4.4.2 but I unlocked and flashed a few 4.4 ROMs to try out (Liquid, CM, OMNI). Anyway, I figured I might want to try a 4.3 ROM so I flashed one. It didn't boot. Went back and installed the 4.4 ROM and all was good. I thought maybe I needed to flash a 4.3 factory image first, so I did. I fastbooted (verb) everything in the JWR66Y directory and OMG it booted. Great, time to flash a ROM, right? Nope. Flashed CWM touch 6.0.4.3 again and it booted using the stock ROM/kernel but after I flashed a custom ROM, it just sits at the boot screen. The obvious answer here would be to have patience and wait. I have waited for 35+ minutes at the bootanimation screen with no sign of booting. This is on any 4.3 ROM I try. However, it will boot right up if I flash the stock JWR66Y system and boot images. What do you think, kernel related or am I missing something more obvious?