Since I kicked off the discussion on shirt fit, I may as well go first.
Here are some old pics of the fit of my Luxire shirt(s). The relevant measurements are:
I have naturally broad-ish shoulders, not much of a chest, and big thighs/seat. Currently I weigh about 82kg, and am trying to get down to around 80. However, even when I do, I think these are going to be a bit too slim. I can get away with it standing up, but they are a bit uncomfortable to sit down in/bulge after a big meal etc. Agree with Nabil - since you spend most of the day sitting down in your shirt, it's probably most important to be comfortable in that situation IMO.
Reading around a bit, it seems that the standard recommendation for a slim fit shirt that still allows for reasonable movement is +3" to the relevant body measurment. At my shoulder size, most places (e.g. HC, O& J, PJ) seem to go for about 20-21" waist measurement. Even at 80kg, I don't think my nautral waist would be 15.75"! I think 17" is a more reasonable goal to reach and actually maintain.
All that being said, I think I might order one or two shirts with the following measurements and, if they work out, send the 5 Luxire shirts I already have back to be recut. It will be reasonably expensive and annoying, but worth it in t he endas I really like the fabrics collars and cuffs on all of them.
Chest Warning: Spoiler! (Click to show)
I think your confusing your measurements a bit. That 3+ inches is an overall measurement to add around the waist, where as all our waist measurements for the shirts are half measurements laid flat, not the total circumference of the shirt . If you add 3 inches on to that you end up with 6 inches of room in total because you double the waist measurement. Does that make sense?