Cutting a jobbridge from nine to six months

Was just looking for some advice. I'm currently undertaking a nine month jobbridge. I know you can opt out of it whenever you want, but might not necessarily get any reference. I'm currently four months into the internship and am working hours well beyond what jobbridge allows. I feel I've learned everything I can from the internship and that it's no longer worth such an investment of time and effort for so little reward.

So...is it possible to get a nine month internship shortened to six months and still get a reference at the end of the six months?

Thanks for any advice!