I saw in another post you do roof inspections. I have a metal roof on my house and regularly do touch and go landings on it. I have had no interference from any of my Vhf/Uhf or Hf ham gear. Now if you are talking a roof a half mile away, you may want something better.
I doubt that pipes on the roof will cause any problems with the control signal. The issue around large metal objects is how it might affect the compass since it relies on the magnetic field of the earth to establish heading. Large chunks of metal can mess with that. Also, getting to close to high voltage lines can cause a problem if you get close enough to be influenced by the electromagnetic field around the wire. If you sense your bird starts acting weird you need to gain altitude quickly to move away from the source. That means only flying where you have an overhead escape path. Flying under overhanging branches or wires might end the flight early.
Find a BIG open field,. Get her up high 50' or so, practice with the GPS off. She holds altitude pretty well, but even a little wind will cause her to drift. Get use to how she responds. This way if you ever loose GPS lock during flight you can be ready for it.
Did I mention she can fly real fast in non GPS mode.
I've been extremely happy with my FPVL antennas...been as far out as 3500 feet and I'm sure I could go further in a fully open area. However, regardless of what you get 3rd party (at least without a signal booster) maintaining video through treelines even with intermittent LOS, your video signal will drop out long before that. I'm definitely planning to add an exterior antenna kit at least as good (no, better) than what the H Pro now comes standard with. I talked with Yuneec CS to inquire if they plan to at least offer an upgrade kit to bring us up to the standard of the Pro ...even for purchase to upgrade the antennas for we early adopters (i.e. beta testers). The response was, "it's been discussed, but doubtful". So, I for one am not holding my breath and am certainly watching and hoping for a good 3rd party upgrade kit, hopefully one that's amplified for telemetry.
I'll just add before someone jumps on me: I'm not interested in flying farther than LOS...but I do want to be assured I'm not going to lose video when flying from behind a treeline, which can be a very regular situation here in Tennessee.
I might be doing that for a company from California. I feel the T H will be a good platform for this.