Note, I have very little clue about how things like vehicles and weapon mounts work. Is a weapon mount externally visible?
I think we're all winging it a little bit on the subject, but the way I'm doing it is Yes. The weapon mount IS externally visible UNLESS you spend the extra money to make it concealable. I couldn't tell you what page or even what book thats in, but there's a cost for it in the chummer program. Wish I could do better for ya.
Is this the type of thing that causes raised eyebrows in polite sections of town?
Yes, depending. External weapon mounts on a military/police/security vehicle won't even draw a second glance. On an obviously civilian vehicle, yeah, totally will draw raised eyebrows as well as possible calls to the authorities. Now, all that being said, Chicago is a little more hardcore, so ya never know.
Do I need a mount on each side of the vehicle or is one on the top sufficient?
Traditionally, weapon mounts are either front facing or rear facing. I suppose you COULD pay extra to have it on a swivel mount, but as for the cost, I haven't a freakin clue.
If you wanted a reference document for prices, folks, SR4's Arsenal book has stuff for all of this, really. A bit of transposition for the prices may be in order. As a personal note, on vans and such, I've been known to put manual mounts on the side doors..passenger gunning spots, in essence

I know I haven't been talking much on here, I apologize. lifestyle has made me need to be choosy on how to spend my time available online (stuff I'm already in with priority, naturally). That being said, I'm working out some stuff for Lyall. Background isn't fully fleshed, but have a gist:
-Daughter of a corp exec (thinking Ares), raised with a silver spoon and all that. not the firstborn, so known that won't take parent's place in the company.
-Decides to enlist service in local military, gets the royal treatment due to family influence. Gets passed assensing filters by payoff ("my kid isn't Awakened, she doesn't need tested, heres' 20K, blah blah blah)
-Is actually a very exceptional soldier, gets put on a special team right out of boot.
-Team gets wasted on one mission because enemy assensing blew their cover. Truth comes out, huge scandal.
-Cheapest and easiest route is to dishonorably discharge, and get disowned by family. Lyall gets put on streets. Disheartened, turns to drinking and slumming.
-Finds food and shelter at various church establishments. Priests there see her Awakened power, decide to help her hone it and develop it (hence the tradition)
-Turns to shadows for lucrative income and tries to scrape by..
Welcome to critiques or suggestions on that. As for connections to the party, she is very much a merc, of the professional and daring kind, and is even prone to a few witty wisecracks in a good mood. Connecting her from a professional standpoint is pretty easy, even location based. Kind of like Rambo, the wandering ex-military vibe going down.
My intent for after the 8-10 year gap in to phase two is that while keeping her soldier skills sharp, she hones and develops her mage-ing stuff, maybe acquiring a lodge, reagents, initiation (MAYBE), and at least one focus. Considering taking a few skill ranks to gain some summoning skill, but I'd imagine that would be minor. During this whole deal, I could see a divergence in personalities, where one side of her is the witty and light-hearted dwarf who enjoys the job, and the other is triggered into this cold, almost crazy killing machine exercising her hatred to the unfair world on anyone unlucky enough to cross her. Thoughts?