Large size of .wmv files

Hi,

I've got .wmv file with 3 minutes duration. This file has ~12MB size. When I put this video to Kdenlive and render this file (with no changes eg. adding effects etc) with option to .wmv (in render window), file after rendering has ~27MB. When I do the same thing (with the same file) in vegas video, file has ~13MB.

Question: How to reduce this .wmv file size in Kdenlive to have similar file size like in vegas?

Settings of my .wmv codec:
acodec=libmp3lame ab=128k ar=44100 ac=2 vcodec=wmv1 minrate=0 vb=%bitrate+'k' aspect=%dar pass=%passes

Video bitrate from menu: 1000k

System:
Ubuntu 10.04

FFmpeg version SVN-r0.5.9-4:0.5.9-0ubuntu0.10.04.1, Copyright (c) 2000-2009 Fabrice Bellard, et al.
configuration: --extra-version=4:0.5.9-0ubuntu0.10.04.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --disable-stripping --disable-vhook --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
libavutil 49.15. 0 / 49.15. 0
libavcodec 52.20. 1 / 52.20. 1
libavformat 52.31. 0 / 52.31. 0
libavdevice 52. 1. 0 / 52. 1. 0
libavfilter 0. 4. 0 / 0. 4. 0
libswscale 0. 7. 1 / 0. 7. 1
libpostproc 51. 2. 0 / 51. 2. 0
built on Jun 12 2012 16:27:34, gcc: 4.4.3
FFmpeg SVN-r0.5.9-4:0.5.9-0ubuntu0.10.04.1
libavutil 49.15. 0 / 49.15. 0
libavcodec 52.20. 1 / 52.20. 1
libavformat 52.31. 0 / 52.31. 0
libavdevice 52. 1. 0 / 52. 1. 0
libavfilter 0. 4. 0 / 0. 4. 0
libswscale 0. 7. 1 / 0. 7. 1
libpostproc 51. 2. 0 / 51. 2. 0

Forums:

If you decrease the video bitrate then the file will be smaller.

Yes, I know about bitrate. But even 400k making .wmv file larger than in vegas.

For example:

Video 1 minute, 320x240, video bitrate (wmv1): 1000k, audio bitrate (mp3): 128k, 1 pass = file has ~9MB (.wmv)

The same settings in vegas = file has ~4MB

Original:
Video: 3min * 60 * 1000kb / 8 = 22.5 MB
Audio: 3min * 60 * 128kb /8 = 2.9MB
22.5 + 2.9 = 25.4MB

Second option:
25.4 / 3 = 8.4

The file sizes are as one would expect from the set bitrates.

So it seems that Vegas can't even calculate! (crapware...)