The final room dimension from screen wall to new back walls is reduced to 4.62m, this results in a viewing distance of about 2.61m to a 3m wide screen, so it is below the recommended minimum I've seen quoted of 1:1 ratio of the scope screen width to viewing distance.
And I see from your drawing that you've got a width of 3.78m?
My finished dimensions, from screen to back wall (with speakers behind screen) should be 4.61m x 3.69m, so almost identical to yours. My side and rear speakers will be slightly into walls.
I have a chimney breast on one side, so you can take another 30cm off the width where the seats are. So where the seats are I've got a width of 3.39m. I've ordered a row of 4 Valencia Verona seats, with centre love seat, which come out at 2.82m. That leaves me 57cm to pass for the back row. I'd actually be ok with 30cm, because we'll rarely use the back row and it's easy to squeeze past a sofa/chair.
My seating distance (eyes) will be about 10' (3.05m). I've then allowed just over a foot to the back of the seats, which leaves 1.2m for the back row. That's enough for the seating I've ordered. Fancy seats at the back would push my front row closer to the screen than I'd like (room nulls and being able to see the screen weave).
Have you got any space from your screen to the front wall? You may want to avoid your ears being at 0.625 (5/8) * the length of your room (you'd get a null at about 600 Hz).
I would have been happy with a single row of seats as this would have been fine for how the room is used the majority of the time. Unfortunately having two rows of seats was one of the non-negotiable conditions of me getting agreement to have the dedicated room. The amount of space on the riser platform means that you can't get past adjacent seats if they are reclined so a more traditional cinema style seat here would be both cheaper and more practical but I'd lose that uniform look that you mentioned.
How the room looks is important to me too. When the film isn't on I'll be lighting up the skirting, soffit, screen, riser steps etc, and I'll have a couple of poster light-boxes. I'm not sure the black rear seats will stand out much in my otherwise black room, and you do notice them, they're still cinema seats.
At the moment I'm finding the viewing distance from the MLP isn't a problem and I'm enjoying the immersion. It surprised me a bit as I wouldn't normally choose to site towards the front of a cinema. I'm running CIH and for narrower 16:9 content the viewing distance is absolutely fine.
Excellent. And if you really needed to make the screen smaller for some fast pace films, couldn't you mask it down? I'll have 4 way masking for mine, for that very reason, although my viewing to screen with is about 1:1.
Not that I had a choice in the end, but due to the width restriction of the room I was a little concerned that if we had gone for a single row of 4 seats then the outer seats on the row would have been pretty close to the surround side speakers. More a problem for the family than me!
When I first planned my room, I anticipated the 4 primary seats being 2 at the front and 2 at the back, but I since learned that the audio at the back wouldn't be good, and the screen size would also be quite different between rows. Get the audio (and video) right for 4 at the front is just easier, and the seats I've ordered aren't too wide, so those at the sides will be far enough off the side surrounds (which will be behind us slightly, and aimed at the furthest seat, so the closest seat is a bit off axis, with resulting lower SPL).
And when it's 3 of us watching, I'm going to push the seats (on carpet sliders) so that we're all closer to the middle.
But if your solution of having the front row closer to the screen works, then that's even better.