So to report back about RXT or marathon.
Diono RXT is the 3rd row, good space for 2 side my side, allowing to add the cup holder in between them. With lionheart seat mats cover the existing 2 holders. The high backs are so high that I placed a small cardboard/foam piece so the pressure would cut into the 3rd row headrest. Latch system works well, just tough to tighten as I had to sit in their seat as well as force them down with my knee. I weigh 155lbs. Finally got them not to wiggle. Seat angles are great as the trip home this evening they both knocked out and the bobble heads rested nicely on the supports vs flopping forward.
Britax in 3rd row, super easy with their click tight system. Both install in about 15mins vs RXT about 45mins. Side by side it's right.
2nd row.
Britax behind passenger, less than 10 mins vs 30mins for RXT (I'll explain more later). Passenger seat push up a lot but will still allow someone 5'10" to fit but tight.
RXT - passenger seat is move up as close to windshield as possible and nearly tilt forward as well. Wife is 5'2" said it is not comfortable and sat in the empty 2nd row. Install, with latch could not get it right no matter what I tried. Then having to use the top tether and passenger seat track tether to finally get the wobbling to go away and secure other wise the RXT was going back. Leg room is much better read facing for our princess vs Britax.
After about 2+ hours of car seat music chairs, we went with 3 RXTs.
Pictures to come.