I would also advocate that you should be able to appeal for a longer period than 7 days.
I think the opposite. 7 days is plenty time, but I think firstly, there should be a cooling off period. i.e. you can't appeal until after X amount of days after the report is produced, say 5. That gives the referee time to digest and process the report, and takes away the initial, not happy and I am appealing it hopefully reducing the appeals coming from emotion.
And then maybe allow 7 days from then to put in an appeal.