Oh and re: what girth to use. It depends on the saddle. Some have long points some have short points. Most dressage saddles have long points though, compared to GP saddles which tend to have short points.
I'd be going for an elasticised girth as they're far easier to do up!!! Also, some girths help to stop a saddle slipping, while others may increase how much a saddle slips, so you might end up testinga few out before you settle on one that really suits your needs.