[X-Newbies] iTunes Resampling Question

[Jane]

Hello all,
I am trying to convert .aiff files from our radio show to be suitable 
for PodCasting.

The problem I have is that I am trying to get the show files to 10MB or 
less.

I start off with a high quality Stereo FM 600MB .aiff files for EACH 
hour of the show.
I am able to resample in iTunes converting to .mp3s @ 24 or even 16 
kbps Mono but still end up with 30MB files. (The people at the station 
do not know how to record them on the CD recorder in anything 
less...there doesn't seem to be a setting for Mono etc)

I just fooled with the settings and got a 4MB file, but it was nearly 
inaudible!
The settings don't allow certain matches between the Sample Rate and 
the Bit Rate...so haven't been able to get the files to sound right in 
a size anything less than 30MB.
Should I set the bit rate lower and quality higher? What is the trick 
here to making it 'allowed' or whatever (that's the alert I get when 
it's not)?

Other broadcasters have their 40 or 50 minute segments at 9MB or so, 
why can't I? Mine are 55 Mins each...and as I said, I think I have cut 
them up to Mono but they are still 30MB.

Thanks for your help. I am all coded and ready to go, except for the 
preparation of these files and I'm 5 shows behind!
- Jane