Hayward SP1070F float valve is too big, but the o-ring is right size?

[Dolm]

I've bought two float valves now trying to get a replacement and both are too big for my skimmer, but just barely - it feels like 1/8" to 1/16" too large to drop flush in the little fins around the o-ring seat.
The lid looks original, and is marked as a Hayward 1070, but there are no identifying marks inside the skimmer itself. It looks like it's fully seated in the pic, but i can feel the gap with my finger tips, and trying to press it down it wobbles cockeye

 

[jblizzle]

I think I would take a file or dremel and put a little notch at each fin rather than keep buying different ones.