I WAS going to notch it originally, but if you look you'd have to damn near remove the whole mudflap to get the hose around. I try to shy away from moving that thing around as it's a royal PITA!
Hell I was even looking around for those D shaped grommets so the round side could fit into the notch on the mudflap and the straight side could hug the frame. That and draining the system isn't hard at all with a handheld vacuum pump. If I remember correctly the entire brake fluid supply fit in the pump, so I could just pour it right back in!
My other thought was notching the front of the mudflap (next to the rear shock), but I wound up shying away from that as well as it just struck me as half assing it
If you do wind up notching yours post some pics por favor!