Tiltalls are great. I use one with my Crown Graphic 4x5 press camera but I wouldn't think of using it with my heavy Sinar P 4x5 monorail.
Even using a lightweight monorail you need a heavier tripod. Just think about it. At one end you have your heavy 300mm f/5.6 lens and at the other end the ground glass and film holder. For close-up portraits you will have your bellows racked out so your weight will be at each end and not directly over the tripod. For close-up portraiture I like a big, heavy monster that is like a rock. Even if I bump into the thing it won't move.