Valance and Backdrop

Ok, back to the layout...  I'm finding that deciding on a valance and backdrop setup is a lot harder than I thought.  I think I've narrowed it down to 3 combinations.  Before I dive into what those are I should define the terms I'm using.

From top to bottom, the valance is the top most piece and serves three roles.  First it hides the light which is typically mounted behind it.  This prevents you from "looking into the lights" so to speak when you look at the layout.  Second it (in theory) gives the eye a "frame" by which to look at the scene.  Think of it as a border around your layout and it draws attention into the layout where it should be.  Thirdly it blocks the visibility of the top of the backdrop in order to keep the illusion that we're not in my basement but we're in another miniature world.

Next the backdrop's ultimate purpose is to prevent distracts that appear behind the layout from being visible.  Really it could be painted a very boring gray and it would do just that.  However it's started to become popular to use it for a second purpose which is to make the scene feel bigger than it really is.  Imagine a set of stunning mountains pushing back to a fading point on a bluish gray sky.  It makes the scene "feel" larger than it really is.

Finally the fascia's job is very similar to the valance.  It frames the scene, giving you a bottom-most border.  It also hides all of the benchwork, giving the edge of the layout a finished look.  Lastly it provides a place to mount controls, control panels, indicator lights, and the like.

Careful arrangement of these 3 things, I'm finding, is a lot more difficult than it seems.

One piece of consideration is the "viewport" which is basically the distance between the valance and the fascia.  This defines the size of the "frame" that people see when they look at the layout.

Another piece of consideration is the line of sight which allows the top of the backdrop to be visible.  This is a relationship between the top of the backdrop, the bottom of the valance, the distance the bottom of the valance is from the backdrop and how close the viewer is standing.  This last one is a bit subjective so it makes it a bit more difficult to determine.

In addition to these factors, figuring out how high to make things is also a consideration.

As mentioned I've been able to come up with 3 configurations and I'm debating between then.  Roughly speaking, these are: bigger valance, smaller viewport; smaller valance, bigger viewport; no valance, huge backdrop.

Bigger Valance, Smaller Viewport
I started here because this is the one recommended by Iain Rice in his book "Shelf Layouts".  Iain advocates a small, 12-14" viewport.  For my configuration, I set this up with a 2 ft. backdrop height and a 1 ft. valance.  The valance is set out from the backdrop the width of the shelf plus 2 inches, rendering a 13" viewport.

I can see why Iain prefers this setup as it gives the layout a much more finished look.  I mean looking at the photo above your eye goes right to the demo train sitting out there.  It feels concise and finished.  I admit, I like how it looks.  The problem I have with this is that with a 13" viewport access it really tight.  Being able to reach in and fiddle with something in the back if needed to seems rather difficult.

If I choose this style, I'm pretty sure I would have to design the valance to be easily removable.  This fact alone would warren quite a bit of engineering work, so I'm really wondering if this is the option for me.

Smaller Valance, Bigger Viewport
Going in the opposite direction, I could make a shorter valance, 7" or so which sets the line of sight slightly higher.  This would warrant a taller backdrop, maybe another 6" or so but still maintain most of the effect.

It doesn't look too bad, right?  However you can already tell the viewport's gotten much bigger, 17" actually, and that 4" addition does make quite a difference.  The scene feels less framed.  On the plus side, it's more accessible.

No Valance, Huge Backdrop
And last is to go all the way, to totally drop the valance (or mount it to the ceiling) and to just make a huge backdrop.  It would only take a 41" backdrop to completely cover from track height to top of insulation.  This would use a lot more sheet material but completely eliminate the need to build a valance and lighting support structure.  The other advantage to this method is that it doesn't "contain" the scene; a backdrop that goes all the way up to the top might feel more open, airy, and natural.  Given that I plan to have taller trees on my layout this might be a much better choice.  Here are a few demo shots.

(Imagine the backdrop goes all the way up to the top of the wall.  I didn't have enough material to mock this up)

So what do you think it should be?
Go with the small viewport for a refined, bordered, "focused" look or go with no valance and a huge backdrop for the open, airy country side look?