So I’ve switched out my son’s drive train. Changed from 9 speed to 10 speed. But I’m left with a wobbly cassette. Pretty sure I need to stick a spacer behind the cassette onto the freehub. I tried with a 2mm spacer but could get the last cog on. I’ve ordered a set that includes a 1mm and a 1.5mm spacer. I’m hoping this should solve it. But am I missing anything else?