Figuring out the best (or perhaps least bad) seat for travel

We've been traveling with a Combi Coccoro, which has been wonderful. Unfortunately, my very very tall 17 month old is about to outgrow it - she has just about an inch of shell above her head. I'm trying to pick a new travel seat (which will also be a backup/husband's car seat), with a few constraints:

1) Fit my 34.5", 24lb. 17 month old rear-facing as long as possible
2) Easy to install, and not require any towels or pool noodles (we tried the Safety First Guide 65, but my husband rebelled when the install required one of these)
3) As easy to travel with as possible, given 1 and 2.

We currently have a Nextfit and Foonf, both of which just seem so darned heavy for travel. I also looked at the Grace Headwise and the True Fit Premier (leaning toward the Premier because it's the lightest). I know none of the tall kid seats are great for travel, but which is the best of the less-than-idea options? Thanks for any help you can provide!

The NextFit sounds like a good choice among the seats you have -- it's not lightweight, but it should fit in most planes and rental cars pretty easily, and doesn't require pool noodles and such.

I personally have favored the Britax Marathon as our all-round travel seat because it is so easy to install in all sorts of planes and vehicles. It's large enough for some extended RF (though certainly other seats would last longer), but yet it is not so large as to be a problem on the plane.

I've heard the NextFit is just as good if not better in that regard, and they are around the same weight, about 25 lbs.

The Diono Radian would be a good choice for extended RF, but it requires a snap-on "boot" for RF which may be inconsistent with criterion #2 that you listed. It's also difficult to fit RF in most airplanes -- though at 17 months and 24 lbs. I personally would be comfortable with FF on the plane because that is consistent with FAA recommendations. You could then still do RF in the taxi or rental car.

A 25-lb. carseat is heavy but should be manageable if you have 2 adults on the trip. My preference is to either wheel the carseat in an empty stroller or (in the case of the Radian in particular) to carry it as a backpack.

If you want something light but long-lasting, the Evenflo SureRide might be a good choice (11.2 pounds). It has a 40" max overall child height for rear facing. A Classic Marathon (16 pounds) or Roundabout 50 (15 pounds) might also work well; lighter than the non-classic Britax seats, but still a very easy installation in any rental car. They can be used RF as long as there is at least 1" of hard shell above the child's head; depending on the child, this may or may not be longer than a seat like the SureRide that has an overall height restriction of 40" for rear facing.

The classic Britax seats used to be Target exclusives; I'm not seeing them on the Target website now. They're still listed as current seats on the Britax website so they must be sold somewhere... I'll come back with a link if I find them!

ETA: [ame="http://www.amazon.com/Britax-Roundabout-Classic-Convertible-Seat/dp/B00GEF7V8Y/ref=sr_1_1?ie=UTF8&qid=1391711759&sr=8-1&keywords=britax+classic"]Here[/ame] is a classic roundabout.

The SureRide is our travel seat and I'm fond of it. I find it less likely to need noodles (though when I travel with a seat that might I just bring a large towel- it doubles as a blanket, etc.)

Hmmm...maybe we'll try the Classic Roundabout. Will it have enough legroom for comfort on a long flight?