Encoding advice for dynamic streaming

Hi

I'm doing af video streaming solution for a larger compagny, but I need some help on whitch bitrates I should aim for, when i encode my videos.

My scenario is as follows:

FMS version: Flash Media Server 4.0

Player: JW Player 5.4 (licenced)

Player widths: 416px and 640px (both 16:9 and with the choice to go fullscreen)

Minimum bitrate support: 250kbs

I need to find out how to layout my bitrates and widths in a way that will:

1. make the switching between to levels (video qualities) as smooth as possible.
2. support a wide range of bw (bandwidth). User with large bw should be fed with a high quality vid and users with low bw should be fed with a low quality vid.
3. support both player widths: 416x240px and 640x340px without doing two different bitrate/with layouts.

I have tested the following bitrate/width layot:

Q5-Q8 is ment for fullscreen view, Q1-Q2 is ment for our small player and Q3-Q4 is ment for our large player.

It works but I'm far from sure that it is the optimal layout. For instance, is it a problem that to videos with different widths have the same bitrate settings or bitrates that lay close to one another?

As far as i know, the player (JW Player) will not choose a video that is more than 20% wider than the players width.

I hope that someone inhere can guide me in the right direction?

Best regards

Jesper