Good luck finding a reasonbly priced Maico rod. I would be a bit concered about the balance of the crank with the longer rod and the larger piston. Atleast with the Yamaha rod it would only be a heavier piston.
I assume you are getting the Maico rod dimensions from the Mitaka list where it lists the big end as 22mm. I hate to let you know that they actualy have a 25mm pin, the list is incorrect. I see there are a few incorrect sizes listed there, use that list with caution.