Originally Posted by
dddd
A steel lock ring must be used, because of the minimal threading engagement with any of these hubs. There is not much more than one turn of engagement,
Ok. So you are acknowledging that the 10sp cassette is indeed wider than the 7 sp cassette and there is barely enough threads to screw the lock ring on.
But you know what- you are on the right track. Some people shave the back of a 11speed cassette to make it fit a 8/9/10 speed hub. You can probably shave a little more off the back side of your 10sp cassette to make it fit the 7sp hub. A bike shop with a head tube facing tool can probably do this for you.