A big step! Cutting tubes, preparing to sew to backing

This is where we need to really pay attention and go slow. Here the time needed to correct mistakes increases exponentially...AMHIK*
We need 7 tubes.
Each tube is composed of two strip sets sewn together - one strip set of each color combination, with a 4.5"X10" end block of the matching color sewn onto each end.
Each tube has two strip sets and four blocks. This makes more sense if you look at the picture. You can't see the blue/water strip set sewn onto the other side of the starry blue/white strip set, but it's there.
We will be cutting the tubes in a staggered manner so that when they are laid out, they will form our pattern.

Here's the method of our tube-cutting madness:


I have a 12"X18" cutting mat that I put inside each tube, in order to cut through just one side or layer of the tube. 
I cut through the solid blue strip sets with the water strip in the middle (NOT the starry blue strip sets with the white strip down the middle).
Tube #1 was cut in the middle of the solid blue half of the tube.
Tube #1 is no longer a tube - it is cut strip set #1. It will be pinned and sewn to the middle of the backing, and the other cut strip sets staggered from there. 
Tube #2 was cut 4" from the center of the solid blue side of the tube (not the starry side). #2 is no longer a tube, but cut strip set #2. Repeat...
Tube #3 was cut 8" from the center of the solid blue side of the tube (and is now cut strip set #3), and
Tube #4 was cut 12" from the center of the solid blue side of the tube (and is now cut strip set #4).
We basically will do the same with cut strip sets #5, #6 and #7, with the measurements matching #2, #3, and #4.
I squared up the edges (trimmed them with the rotary cutter so they are even). Feeding the OCS monster again :)

*ask me how I know