Don't worry too much about making the cut-off in training, I've purposly never tried this as I know I won't do it without the pressure of racing so if you get within 15mins or so your probably going to be ok.

The route after Mam Nick can get very lonely when the clag's down, it's cold and wet and you can't see another soul, this is when you need to dig in and keep going. I think this is why they ask for relevant experience rather than just being fit enough to cover the distance and make the cut.

Good luck, hope you get in.