New and Freaky With a Side of Hope

My mouse broke. It actually broke several months ago and I glued the piece back into place, but I really don't want to keep gluing it, now that it's loose again. So I got a new mouse, tonight. It's optical. It's also so much more sensitive than the old one that I can't get my arrow onto anything to click.

The mouse is awesome, but the real reason for going to the store was to test car seats. Again. This was Target, though, and not BabiesRUs. They don't let you test the seats in your car at Target. Even so, I think I might have found a winning combination.

Here's the infant seat we've got our eye on. It's the Baby Trend Flex-Loc and it's only 16" wide.
This is the most promising car seat. It's the Cosco "high-backed booster" and is 17" wide.

The reason the car seat looks so promising is that there is a ~1" overlap where the lip of the infant seat slides over the edge of the car seat's seat, effectively making all of the car seats 16" wide. The back seat of my car is ~48" wide. Follow the math and you'll see the light begin to dawn.

Target also sells this, the Cosco Pronto booster, but it wasn't in our store so I didn't get to test (or measure) it tonight. It's main bonus feature is that it starts at 30lbs and 34" (it fits Elena) but I don't know if the arm rests will flip up to make room for the infant seat.
We're going to see if we can have a discussion with a store manager to test the car seats out. If the manager lets us, and they fit, that's a $200 sale and a very grateful customer. Frances, you know people, right? Can you help?