Just discovered that as soon as I research Impulse engines, I have a choice for what goes into a colonizer. I can either build a Speed-6 colonizer (like I used to do) with a short range, or I can build a Speed-5 colonizer with two basic life support modules.
Don't know exactly when you put that in there, because I was so used to just using my upgrade to speed-6. Great to be able to build more than one kind of ship.