Loom knitting a beret

Hello, my name is Pat from South Africa. I have been looming for about 4 years now, not often though. My experience in loom knitting comes from you tube. So I decided to knit this beret for my daughter. The instruction for this piece, starting with the brim, and done on a 41 peg knifty knitter is to knit 50 combos of K and P. for 5 pegs. And is to be 70cm long. Here is the problem. I used 2 strands of DK, single strand and even bulky yarn. It never came near the required length.The finished brim measured about 42cm. Can you please help?
Thanks, Shepa (Pat)

Welcome to KH!
Perhaps a loom knitter will be able to help out.
@Daz or @tattfae or @WhampusKitty