ulimate wheel wobble thoery(Thery,Thoery?)

I learned how to ultimate wheel last month,and i can freemount,rolling mount,jump mount,ride in circles,ride down little hills,and hop in a dorky looking hunched over position,but i still cant ride consistently for over 150 feet or so.I think its because my “ultimate wheel” is really just an old wheel off a old junker uni,and when i ride the wheel wobbles back and forth crazily between my legs making me fall off alot because of the wide cranks.the ultimate wheels at uni.com dont have cranks,just pedals,therefore making it narrower.Is this easyer to ride,or do i just need to practice more?

it will be easier if the pedals are in closer

although, I’m sure like everything else, practice makes perfect.