Question A New Addition - need help w/ 2 rear facing

2012 Buick Verano -- 48" Back seat
Britax Marathon G3 base JUST FITS in the center seat
Ideally I will have a RFing seat behind the driver and one in the center. I have tried the Scenera and Marathon side by side and can not get a good install.

2006 GMC Sierra EXT Cab
Wide across, very very tight front to back.
I currently have a Cosco Scenera in the center, but it's about 6" too big to fit outboard. I have installed the Marathon outboard but it does not fit front to back without the passenger being extremely uncomfortable.

So my son is currently 2y8m and very petite. I would like to avoid putting him forward facing in our truck if possible. New baby will be here (we are shooting for) next November. I want to start with a convertible, I'm thinking the newborn could use the Scenera RFing in the center in our truck ---- and we could get a new (hopefully convertible) for my will be 3.5 year old.

Am I being crazy? Should I just bite the bullet and get a combination seat for him when the time comes? Is there a seat more compact front to back than the marathon? I wouldn't be opposed to getting a Coccoro ---- but would it be feasible to just get one and move it back and forth? I wouldn't even be able to count on my almost 4 year old fitting RFing anymore, would I?

Is a guide 65 good for us? I'm not wanting to break the bank. Would a Coccoro (for baby) in the center of the Buick with a Guide 65 next to it? Then maybe the Marathon outboard in the GMC (as close to 30deg as I can get) with the Scenera in the center for baby?

I expect our future child to be 5-6lbs but not premature.

In a tight fit situation, I wouldn't hesitate to turn a 3.5-year-old, neurotypical child FF (if that is in fact when your new baby arrives).

The Guide 65 is a great seat if you can get it to fit and install securely next to the Marathon AND if it fits your child well.

Maybe I will FF in my truck.

I was looking at the Baby Trend Hybrid 3-1 seat for him at that point for that vehicle. Or else try our Marathon RFing (perhaps more inclined) and see how that works in the truck next to the Scenera. Will the scenera work pretty much from birth? The recline stays the same regardless of age, correct?

Guide 65 or Diono Radian R100 (center) and a Combi Coccoro outboard for baby in our Buick?

I tend to steer parents away from the BabyTrend, as it's a very difficult, confusing installation, with guidelines that change depending on weight/tether/etc. I've seen technicians - multiple technicians - install this seat incorrectly. If you opt to use it, be certain to follow the instructions VERY carefully, check and recheck it, and maybe even see if you can get someone carseat-saavy (ideally an experienced tech) to put a second set of eyes on it. I'm sure it's a great seat if properly installed, it's just getting to that point that is difficult. The Evenflo Maestro is around the same price point with similar top slot height and a 50lb harness rating, or a Harmony Defender is quite slim, just a smidge more money (maybe $10 more) and has a 65lb weight rating with similar top height, if you are looking at other options. You could also consider the Evenflo Titan65/SureRide, which would enable you to rear-face if it fits or forward-face if it doesn't... no booster capacity but it will last forever harnessed.

In your truck, you should probably be able to get a Radian next to your Marathon. Or, maybe, the Scenera. If you put it in with the angle adjuster, it might fit.

Carseatblog has a great article on front-to-back comparisons, but I can't link it right now as my workplace has CSB blocked (considers it a "blog.")

Here's the link to the carseatblog.com convertible carseat RF front-to-back space comparison Carrie mentioned: http://carseatblog.com/22818/the-ul...ertible-space-comparison-review-size-matters/

I have no experience with the Coccoro in either of your vehicles, but we have one of those seats and it is super light and easy to move. Assuming you can get a good install in your vehicles, it shouldn't be a problem to move back and forth. That's what we use for our babies until they outgrow it.

I would also try a Radian with an angle adjuster.