What are the specs. required from that Web site, that you are uploading to?
The determining factors on File Size are Duration (you are set to 00;10;00;00) and Bit-Rate. Quality is directly tied to Bit-Rate, so as the Bit-Rate goes down, so will quality. How much of a loss is too much? Only you can be the judge of that.
Some CODEC's "appear" to do a better job with allowing lower Bit-Rates, with higher perceived quality. However, the hosting Web site may, or may not be able to use material with them, hence my first question.