Cheers Deeno
Thanks too Greg. The Polarie has a "1/2" setting, specifically designed to let you fudge this. You slow the star field's rate by half, and induce a half sidereal rate movement in your foreground. Theory is that meeting half way for both you can get away with it for short exposures without over-blurring either too much.
Attached - an example I hurriedly took the other night. This was a quick 75 second test shot at high ISO just to see what would happen.