Very good proposal. Hope I'll find a way to determine when the GPRS connection is canceled and connected new. Because the rounding happens exactly at this point. If I'm not able to catch this event it makes no sense to add an option for the minimum data block size.

For example: My provider drops the connection every 02 h 30 minutes. And at midnight. I'm quite sure, that the rounding to the next data block size happens at these very moments.