yes, too much moisture loss will result in a flat and over-developed cup. Too little moisture loss can result n harsh/sharp flavors, you'd have to drop it really early to have less than 10% though.
With the filter, even if it's not deteriorating, your roaster is always going to perform better when the filter is clean. This is true for every roaster, home to commercial. Most commercial outfits (who are doing it right) have weekly and monthly cleaning schedules in order to keep the airflow efficient. Airflow is very important in coffee roasting, and even a little build up can have an affect on performance. Don't have experience myself with the hottop, but I'm sure someone could chime in and back that up.



