What's the Circumference of the Penumbra of the Recessed Lights?

Geez, I wished I had asked that last Friday! The electricians were coming in tomorrow to install the recessed lights. I'm supposed to mark the spaces on the ceiling where the lights are to be installed, or leave a map for them. Sandra and I literally spent two hours sticking
and resticking post-it's to the ceiling to see what the light pattern would look like.

The things we were considering were:
How would the set-up look overall?
Would it provide enough light for the room as a whole?
Would it provide enough light to each section of the room?
Is it functional to place a light there?
Is it aesthetically pleasing to place a light there?
Should they all line up a certain way?
How far from the wall should they be?
How far from each other should they be?
The ceiling's 10' high. What would be the umbra and penumbra of the lighting cone from that distance?
Where should the switch be? Should the switches both have dimmers?
Is it necessary to have three switches - one for one of the outlets?
Based on the dimensions of the room, if we placed them evenly into two rows of three, how would it look?
Should each pair (front and back of the room) be on the same plane?
Should each set of three (front three, back three) be on the same plane?

Sandra diligently helped me take notes as I read off measurements, and in the end, here's what we got:


There's about 72" between the front row and the back row.

We left that Post-It, along with 6 on the ceiling where each light should be for the electricians. Each Post-It on the ceiling had the distance to either side (wall or light) with arrows pointing out the direction. I really hope it's clear enough for them! They're supposed to be in tomorrow. I'll stop by after work to check it out!