I'm jealous, I love Haldane wheels. I don't think the pitch of the treadle would suit me though, I'd have to have it flatter for less ankle strain, hubby altered my Lewis for me.
Did you know that Haldane made different sized double whorls for their wheels? Its the only way to alter the ratio with double band wheels as far as I know, but they are handy for different types of spinning, nice big one for soft thick yarns and tiny one for fast fine spinning and long draw. If you don't already have these it would be worth looking out for some if you like fast spinning.