take a look at this here thread
Saw a least one guy on a Cannondale with Lefty at the Ae round, most of the trails are on red grade level trail centre type tracks, with the exception of Ae which used the Downhill track for seeding and the final stage… i imagine Innerleithen will be farily gnarly too.
At the end of the day, its less about the bike and more about riding at a level you feel comfortable with – there are guys on hardtails beating folks on 6 inch all-mountain bikes, and most of the time there are routes around the bigger drops… I say give it a go, you’ll probably enjoy it!