Sunroof adjustment

Hi can anyone tell me if the steel sliding sunroof can be adjusted front to rear?. The gap is too tight at the front at the moment. I'd read that the stops for the sliders can be moved but I can't see how. They would need to move rearwards around 3mm.

 Here's a link to an online workshop manual I found showing how the front/rear gap can be adjusted;

Volkswagen Workshop Service and Repair Manuals > Golf Mk1 > Body | Body repair work. | Sliding roof | Sliding roof / exploded view - Golf, Jetta | Adjustment operations on the tilting roof - Scirocco

I'm going to have another go at this today. If anyone has done this before I'd really appreciate some feedback on how you got on, thanks.