We have successfully appealed for a place at FSG this year for our dd2 ( dd1 gained a place last year )
According to the Executive Head and one of the Deputy Heads we spoke to following our appeal they had 68 places available and less than that in appeals. However they also stated that not all of those that appealed were successful.
Personally although we found the appeal process very stressful the panel were very nice. They were very thorough and really made us provide a lot of evidence that our dd was at the right level academically for the school and spoke a lot about not being willing to put girls in her were not going to be able to achieve well.
Hope this is helpful to you. Unfortunately I know nothing about Dover grammar.