Monkey rockers do not have flat seats. They have a "bucket" contour that cradles your glutes and thighs. Look for plans that include a contour gauge or grid coordinates for shaping the seat.
: Using body-safe, non-toxic finishes is recommended for furniture intended for close skin contact.
Many vintage predate modern ASTM F963 (toy safety standards). If your plan shows a sharp point on the monkey’s ear or tail, round it off immediately.
Standard plans fit a person up to 6’0” and 220 lbs. "Big and tall" monkey rocker plans increase the width of the seat bucket to 22” and use double-thick laminations for the rockers.