Sorry I didn't get to this sooner.
Busy!
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Here's my stab at the questions -
(1)
There's just no way to tell, without first-hand testing.
The problem is that each individual vehicle presents very different LIDAR profiles, and that the protective capabilities of VEIL not only varies somewhat with application, but to a greater extent with the actual LIDAR threat hardware - and this thus creates a set of variables which makes the entire situation totally unpredictable.
(2)
There's *ALWAYS* a possibility for a good detector to pick up laser "scatter"/reflections.
This is why, regardless of how complete your jammer setup may be, you still *always* need a good laser/radar detector to insure proper protection.
Although he 9500i isn't nearly as sensitive of a laser detector as the V1, I've still gotten advanced-warning of laser traps via the detector being high-mounted in my car...and yes, this is even advance detection that came online *BEFORE* any of my jammers activated.
This, combined with the fact that police LIDAR is not as "instantaneous" as it has led us to believe (although the vast majority of vehicles targeted at typical distances do return with a reading "near-instantly" [quoted is 1/3 of a second], there are many instances where a lock takes longer, or may only be achieved after a significant delay or not even be achieved at all - and yes, these instances are totally
RANDOM, and without even a jammer or passive protection of any kind being used [so you can imagine what kind of additional protection you can get, with passive and/or active measures undertaken/engaged), means that you do have a small window of opportunity, and a good detector can help you exploit this window.
The catch here, though, is whether you can "count" on such a save, and unfortunately, the answer is a resounding "no."
A part of the problem is, indeed, in that your chosen hardware (which you have no recourse for, I understand, as you require detector-"stealth") is just not optimized for this particular threat - but also, a part of the problem is inherent in the placement of the detector itself.
Yes, high-mount will offer you the best chance to catch scatter/reflections as well as "down-road" LIDAR-spread (from enforcers painting vehicles ahead of your lane-of-travel), but at closer ranges, it is very possible for the high-mounting to also work against you - it's entirely possible for the detector to simply "miss" the incoming beam, at such close ranges.
If LIDAR is a serious threat in your area, your only viable solution is a good active jammer.
(3)
I am much less optimistic, here, than the person who PM'ed you.
Honestly, if you've got the money for a dual-head setup, *UNLESS* your locals are known for rear-engagement, I would completely bias your protection to frontal-only, and use a dual-head setup, up-front, to maximize your best-odds against such threats.
At closer ranges, two heads are needed to insure coverage.
And no, it's not about "95% of the time," it's not even about "99%" of the time. What you don't want is *any* possibility of unexpected PTs. And in this respect, even with the most comprehensive jammer coverage, even if you elected to also incorporate layered defenses such as passive measures, there will *always* still exist the chances that a trap will catch you "just right," and that you'll get a ticket. It's just a part of the game, and is unavoidable.
What instead should be pursued is maximizing your odds at successfully effecting sufficient jamming to avoid a citation - and that just means stacking as many things in your favor as possible. Thus, if you have the money for a dual-head set-up, and your locals are not *confirmed* for rear engagements, don't bother with the rear (where, honestly, you'll need *at least* two heads, with even more thought to placement/spacing), just "max-out" frontal coverage.
And IMveryHO, no, one head, up-front, is not sufficient to effect "more than enough" coverage. It's just "adequate."
[
Also, let's examine your original qualification of "2-seconds" warning time. The obvious question here is two-fold: "at what speed," and then, "at what distance?" Are we talking about a scenario where the initial engagement is at quarter-mile, at travel speed of 70 MPH, or are we talking a situation where initial engagement is at less than 300 ft., at 50 MPH? No need to answer this question 
- I think you can see where the "2-seconds" fails. This is just to illustrate the problem underlying this kind of thinking, that's all. ]
(4)
Purchase a new one from an authorized reseller/retailer. That's the only way you can be sure you're getting the right product.
Alternatively, purchase one from the secondary market from a "known-quantity" enthusiast/hobbyist, and educate yourself as to how to tell the difference between units which are "100-PPS UL enabled," as well as purchase testing equipment (i.e. SpeedLab's Laser Jammer Tester) which allows distinction between the 100-PPS UL, versus other LIDAR threats.