Hanging recessed light housings

I am beginning to hang my recessed light housings (not remodel but new work).
I laid out the desired spacing and location in CAD, and when it comes time to install, I ran into a few challenges. Right now I am struggling with a set of 9 lights.
I put in the first, second, and when it comes to the third, the joist is right in the middle of where I want the light to be, so it won't work. Which means if I want the light to be spaced the same, I need to move the second light. I can slide it along the flange, but if it's already butt up against the joist then I can't slide it. Furthermore, by sliding the second light, the other two rows will need adjustments as well. Basically, to run into trouble positioning one light, there is impact on the positions of many others. I have nine in the living room, eight in the dinning room, and six in the kitchen and since it's all open, they are all aligned with each other, so I decided I will need to plan it out better before I start hanging the lights.
So what I am looking for is tips on what the best way to hang them. I started to mark them down on the floor, since there is no way to mark them on the ceiling (ceiling sheet rock is down). Now when I start to hang them, how do I align where it is on the floor to the location on the ceiling? Do I use a plumb-bob?
Even though the ceiling is down, the fiber glass insulation is still there. I need to trim the insulation back a few inches since what I got are Non-IC housings. What is the best way to trim them? A pair of scissors? or just rip them apart?
Another question is what if some insulation get too close would that start a fire? These are fiberglass insulation I think they are highly flammable.
Last question is once I have all the housings wired, in order to test them, can I screw the bulbs in without putting in the trim first - just to test?
Thanks,
MC
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*Welcome to my world. Happens all of the time. Basements are the worst because of gas and water pipes and ducts.

*There are laser levels and sights for transposing from the floor to the ceiling. I usually lay it out on paper first. You can tweak the distances a little and it will not be perceived on the finished ceiling. As I have mentioned in other posts no one really takes a good hard look at recessed lights.

*I just use a sharp razor knife.

*I've never encountered a problem. Do the best that you can. You only need to stay back 3" and no insulation on top. The non-ic units are rated for 150 watts and that is what the requirements for keeping the insulation away are based on.

*Yes. I sometimes put in regular or rough service bulbs so that there will be light for others to work in the room. Save the good bulbs until the job is done and the trims are in.
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I had a similar situation but fortunately it was only a few inches. I went ahead and mounted the lights as close to 'plan' as I could and it is hardly noticeable that they aren't perfect (although I know!).
The other option if it is too noticeable is to come up with an arrangement that doesn't put the lights in a straight line. IE if you have 2 rows of 3 lights each, have the two on the ends of each row 5 feet apart while the 2 in the middle are only 4 ft apart. that keeps the eye from 'drawing' the straight line between the lights and noticing the variance.

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I am glad that I had the ceiling down so I can see what's going down, between the studs and ceiling furring strips and EMT conduits, if I had used remodel cans, even with a stud finder it would be very difficult to figure out the pattern not knowing what's up above.
Yesterday I was trying to wrestle with the kitchen counter lights, and as John recommended, switch to 4" (Halo H99T) made it easier and I was able to place three H99T cans 32" apart, evenly, although not centered to the room or center to the big window. It's strange that the joists are spaced 24" apart, the room kitchen is 140" wide, I could not easily find a spacing (tried 36", 38", and just about every increment) using the center of the room as the middle light, or the center of the window as the middle light, had to shift over before it would fit.
I suspect when I get to the center areas where I have the three pendants over the kitchen island, which is aligned with the 9 lights in the dinning room, which is also aligned with another set of 8 in the living room, I will have even more trouble...I briefly toyed with the idea of completely random spacing, this way no one can tell if it's off.
MC

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