Hi Issy,
Congratulations on your RS Aero (nearly) and welcome to the Class!
The I recommend 105cm which is now the standard supplied in both carbon and alloy from RS. RS' carbon ones are great. you should add that into the deal.
Righting lines are very useful if you have a short reach and can not easily reach the gunwhale as the boat starts to come up as you put weight in the daggerboard. A lot of smaller people do use them, but reach length is more an issue than weight without the lines.
For every which way to recover an RS Aero check out the 'Capsize Corner'
thread in this forum HERE , together with a video demo there of the first righting lines.
