So I got my flat patches in the window, and I can confirm I have functioning VHF and UHF antennas outside, hooked up, and live. But... it's far from sketchy! The flat cable honestly has held up way better than I thought it would (at least for now) but I still dont completely trust it. I'll be getting some SWR/Power meters soon for that reason. (All I currently have is a nanoVNA I use to read SWR.)

I'm running a Firestik 2MCKB 4 Ft 2-Meter Base Antenna with around 30ft or so of LMR-240 for VHF, and the default Midland MXT500 antenna (and attached cable) for UHF. The performance has been pretty good, not great, but good enough to make a couple contacts and get into repeaters. I'm definitely losing some signal somewhere though. When the 2m antenna was inside, I was picking up like 4 of the weather channels at the same time; I haven't tested how many with the new rig though.

I'll keep you guys updated on the progress of this project!