You can use flex braided lines but they are a bit pricey for the whole system. I think the general feeling is that the pedal will be a little spongey as the teflon liner expands. We have a lot of flex line on the sand buggy and the pedal is a bit spongy but we have only a 5/8" MC so there isn't much fluid displacement.

I have all flex lines onsthe rear end and a 36" line to the frame on my Willys. Total of 5 flex lines and my pedal is rock hard.