Dumb questions about mobile antennas for my BCD436HP

[Firekite]

Hi all, hopefully this will be short and painless.

I have a 2011 F250 that I plan to install a 3/4" NMO Mount in the center of the roof, with a Larsen NMO150/450/758 mounted on it. I need to be able to scan everything from 155Mhz to 860Mhz. I was looking at the Larsen NMOKHFUDSMAI for the NMO, with 17' of RG58/U terminating in an SMA connector. I mostly run empty but also pull a 5th wheel.

What I'm trying to figure out is a few simple things:

1. Is there anything magical about the 17 feet of coax? That's almost certainly longer than I'll actually need to reach the scanner. If I need to coil up the excess, does it matter where and how?
   
   
2. If there's nothing magic to a specific length of coax, would I be better off cutting the antenna down to more or less exactly what I need when the scanner is mounted in the truck (with a little slack) and attaching a right-angle SMA connector or simply letting Larsen build it for me? I've never made my own coax before, but I've watched others do it, and I've crimped innumerable network and phone cables over the years and soldered basic stuff like aftermarket car stereo harnesses, so I feel like I could figure it out if I needed to.
   
   
3. If I just stick with the Larsen pre-made SMA cable, is there any harm in using a right-angle SMA adapter? Something like this in nickel or gold? Not sure how much difference the material makes.
   
   
4. If I put it in the center of the roof, and then eventually get off my butt and get into ham stuff, I'd most likely simply put an appropriate ham antenna in that spot instead. For a scanner antenna at that point, could I simply put another NMO at, say, the back of the cab roof, still in the center? Or should it be placed differently? This is just a hypothetical curiosity for now.
   
   
5. When moving from handheld use to mounted in the vehicle, do I need to power down the scanner, then remove the portable antenna and attach the mobile antenna before powering back up? Or is it kosher to just remove one and hook up the other?

Thank you for those who know and are willing to share!

 

[Hit_Factor]

1. No
2. Yes
3. Not much, there will be a small loss, probably won't notice a difference.
4. Separate as far as possible. My Icom id-5100 antenna is 2.5 feet away from my sds100 antenna.
5. No