Just wanted to chime in here on a few things.
In our '14, the manual clearly stated that if you use the LATCH system on the rear passenger side, you CAN NOT use the middle seat belt for ANYTHING. This is most likely because of the restraint system setup. They must have changed something with the '17 (or possibly a model between '14 and '17) because the manual does not show any restrictions with the use of LATCH and the middle seat belt (which is good for me as I'd rather use LATCH over the belt). The restraint system does look like it's been redesigned because of the previous limitation.
I have a Chicco KeyFit 30 with the base installed using LATCH behind the drivers seat. Behind the passenger is a Graco 4ever with the seat belt (I will be changing this to the LATCH based on the information I provided above...my '17 is only 5 days old so I was going off of the '14 info).
With this setup, my wife and I can *somewhat* easily sit in the middle seat and provide a visual aid for our 4 month old when necessary (we've all been there, right?!). I am 5'10" 200lbs. My wife is 5'8" and significantly lighter than me.
My wife has a '13 Passat with the KeyFit base and a Diono Radian rXT. I am going to be swapping the Graco/Diono for a couple of reasons:
1) The Diono is slimmer and does not sit on an backward incline like the Graco. Graco recommends position 4 for forward-facing under 40 lbs. (Daughter is almost 4 and just under 40 lbs.) and it can be a little uncomfortable for her, especially on longer rides. The Diono is not adjustable and while it will still have a slight backward because of the seats, it won't be nearly as much as the Graco.
2) I back into the garage on the left side (passengers side along a wall) and I have the car seats set in a way so that when we leave the house on days my wife works, my daughter can either climb or I can lift her into the 4R and then sit herself into the seat and buckle the chest strap and then I can drop the KeyFit into the base. I fire up the 4R, pull out of the garage and then strap my daughter in (don't worry, we never forget to strap her in and she's not shy of reminding us even when we roll forward 3 inches). The Diono will allow her to: climb in more easily, give her some more leg room, and give the middle seat a little extra room for A) passengers and B) lowering the middle seat in the event I bring home something long.
A couple of safety tips. If you use seat covers, ensure your car seat's manual states it's OK to do so...Remember...They've done the testing, not you! It's also generally best practice to ensure that no part of the car seat is touching the seat in front or beside it (again, double check with the manual(s)).
Last, but not least, be safe and read your car/car seat manuals! We're responsible for our kids safety!
EDIT: For the Diono convertible seats. When you're rear-facing and if you find that the angle is too steep (it usually is) to either properly give your child or front passenger/driver comfort, get an angle adjuster:
https://www.amazon.com/Diono-60320-...02296562&sr=8-1&keywords=diono+angle+adjuster