We are also considering appealing for STRS for the same reason as you but our DS has 2 points below pass mark.
We however do not know what our DS score was on each paper as yet or how to get this information at this stage, I have called school for an appeals pack which is yet to arrive.
My DS applied to Crypt as well as STRS so although we don't have the marks for each paper we do have the score against the Crypt cohort for each.
We have the STRS appeal pack but there's not much additional explanation - just a copy of the school's admission criteria, a document explaining the appeal process (identical to the one on Gloucestershire's website) and an appeal form.
Good luck with your appeal if you decide to go through with it!