AFAIK there's no racing line that cuts the corner to MW stones - there may be a trod but I doubt it gains anything significant as it doesn't cut a very big corner and is likely to be quite heathery and tussocky.
The 'race line' on Win Hill is nicer IMO as its not as undulating. Its fairly easy to pick up, there's a little trod on the LHS just after a little knoll as you begin climbing the whale back of Win Hill.
The main shortcut that is worth seeking out is the one that runs from near Pym Chair to the top of Crowden Brook avoiding the woolpacks.