Bit confused here.. your fourth alpha is 41 MB, i took a look in the bsp and it seems you only have a dozen cubemaps or so, two models with no textures and a skybox texture..
So how the heck is it so large
lightmap scale 1 on all faces???
skybox is 5mb, cubemaps are 2mb, entities are 240k, it seems lumps 8 and 53 take up most of your space (10mb each), which are *Cracks open the VDC*
...... (drumroll please)....... Lighting and Lighting HDR
Lump 40 is close after at a little under 8mb which is the pakfile
and lump 4 is the last one to take up more than 2 mb (3) which is vis information.
Now lets open a similar map for comparison, say, plr_cornfield_a6 wich uses a custom sky and is probably at a similar level of visual detail.
Cornfield is totally 36 MB
1.5mb for a sound
2mb for my custom dev textures... (he didn't delete them from his PC so pakrat automatically paks them in... doh!)
Only one cubemap.
About 2 mb for some other textures for his cart
4mb for my skybox
His biggest lump is 40, at 13mb (pakfile)
8 and 53 each at 6.7 (lighting + HDR)
His next biggest is 29 which is some physics ino, his vis (4 ) is at .5mb
Since you probably dont know what lump 40 is, the pakfile (well i didn't) it's basicly all the content packed in with pakrat.
Just some food for thought.