Another thing to factor is compression over RAS. Modems will automatically compress the data stream so pre-compressing the data negates that.

If the data were pre-compressed on the far side(where the data is) and uncompressed locally, a small improvement may be realized, but if the compressing/decompressing is done on the same side, the bandwidth will increase rather than decrease.
_________________________
Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.