You must mean the Gardner float? Not Korda?
If thats what you mean, I would guess u can (and should) use thicker line than most use during normal floater fishing since its simply just not necessary to use a thin line for descretion. If the carp cant see the line and all you might as well go safe and take a stronger line, in my oppinion.
Ive never tried them myself so havent tested the matter. However From what I can see on pictures I am quite curious myself wether the design of the float itself might as well spook fish or make them uncomfy enough to not take the bait. After all, the float is just next to the bait at all time. Seems quite "suspicious" to me.
14.5 metres of carbon fibre over there heads didnt spook em
But as said by sgart the size of line isnt an issue m8 theres only the bait on the surface