I currently use a 550 grain skagit line with 15ft windcutter tips on my 4 piece Guideline 13'7'' le Cie #8/9 MF rod in high water with no problems. In low water I would use an 8/9 or 9/10 floating integrated shooting head.

I used to own a 3 piece 14'7'' le Cie, but only used shooting heads and spey lines on it . I sold it as it was too long to fit in the boot of the car, but it was a lovely rod and I enjoyed fishing with it.