Actually spark - old owners keeping 10% seems to be a standard trait of buying a shell - at least from my experience.
In the last year I've talked to about 15 shells trying to find a decent buy. They were priced from $40k thru $200k, with most about $200k. And they ALL wanted to keep 10% of the shares.
Needless to say, I didn't buy any of them.
Those who believe without reason... cannot be convinced by reason