Our league uses RIF balls for 8U (10") and 10U (11"). This seems pretty consistent with other ASA leagues in our area. From my observation, the transition from RIF to Dream Seam (or equivalent) is not a significant adjustment as far as ball bouncing dynamics.
Yep same here for 8U - its the 10 inch RIF 1 DOT (the one with the blue dot thats soft).... the 10U is 11inch but I think its a little harder (not as hard as the dreamseam but not as squishy as the RIF 1 DOT.. sorry cant remember exact ball type for 10U)